Blueberry Pie Bars with Lattice Crust

If you popped round right now, I’d probably press a still warm square of these blueberry pie bars into your hand and not even pretend to be patient about it. They’re the sort of bake that makes the kitchen smell like a tiny summer fair, even in January. The first time I made them I got distracted by a neighbor’s cat staring at me like I was stealing its blueberries, and the lattice went a bit wobbly. Guess what. Still tasted lush. And honestly, that wobbly lattice looked kinda charming.

Why I keep making these when I should be folding laundry

I make this when I want pie but also want to eat it with my hands — less fuss, same cozy feeling. My family goes a bit mad for the buttery base and jammy blueberry filling, especially the edge pieces; those chewy corners disappear first. And when I’m short on time, I can press the bottom crust right into the pan without rolling. I used to dread lattice tops because they felt like a test I hadn’t revised for, but actually, I find it works better if I stop overthinking and just weave like I’m making a paper placemat at school. No one has ever said my lattice was too casual.

What you’ll need, give or take

These are the ingredients I use most days, but I’ll note a few swaps. Because real life.

All purpose flour: 2 and 1/2 cups, about 300 g. My grandmother always insisted on a certain blue bag brand, but honestly any decent flour works fine.
Granulated sugar: 1/2 cup, about 100 g, for the crust. I sometimes use light brown sugar if I want a little caramel note.
Fine salt: 1/2 teaspoon.
Cold unsalted butter: 1 cup, 226 g, cut into small cubes. If I’m in a hurry, I grate frozen butter and it’s brilliant.
Large egg: 1 whole, plus 1 yolk for richness. If you only have one egg total, it’s okay, add a splash of milk to help bind.
Vanilla extract: 1 teaspoon. Optional but nice.
Blueberries: about 4 cups, 550 to 600 g. Fresh or frozen. If using frozen, don’t thaw all the way, just loose the ice crystals.
Sugar for the filling: 1/2 to 2/3 cup, 100 to 130 g, to taste.
Cornstarch: 3 tablespoons, about 24 g. I sometimes use 4 tablespoons if the berries are extra juicy. Arrowroot or quick cooking tapioca also works.
Lemon zest and juice: zest of 1 lemon and 1 to 2 tablespoons juice. Lime is a cheeky swap.
Ground cinnamon: a pinch, optional but lovely.
Coarse sugar for sprinkling: a handful, like turbinado. Not essential, just pretty.
Milk or cream for brushing the lattice, or a beaten egg if you want extra shine.

Substitutions I actually make: Sometimes I use half spelt flour for a nutty vibe, and once I swapped in a dairy free butter and it was fine, just a tad softer. If you’re out of cornstarch, flour works, you’ll just need a bit more and the filling will be cloudier, which I dont mind.

Let’s make the blueberry pie bars with lattice on top

Heat the oven to 350 F or 175 C. Line a 9 x 13 inch pan with parchment so the paper hangs over the long sides. Easier to lift later.
Make the dough. In a big bowl, whisk the flour, sugar, and salt. Cut in the cold butter with a pastry blender until it looks like coarse crumbs with pea bits. No pastry blender? Two knives or your fingertips work. Or pulse in a food processor, but stop before it turns sandy paste.
Whisk the egg, yolk, and vanilla together, then drizzle over the flour mix. Stir with a fork until clumps form. It will look a bit shaggy at first — don’t worry if it looks a bit weird at this stage, it always does. Squeeze with your hands and it’ll come together. If it’s dry, add a teaspoon of cold water.
Divide the dough. Press about two thirds of it into the pan in an even layer. I use the bottom of a measuring cup to tap it flat. Chill the remaining third for the lattice and pop it in the fridge.
Par bake the base for 10 to 12 minutes, just until the edges look slightly set. This keeps the bottom from going soggy. This is where I usually sneak a taste of a crumb at the corner, no regrets.
Make the filling while the base bakes. In a bowl, toss the blueberries with sugar, cornstarch, lemon zest, lemon juice, cinnamon, and a small pinch of salt. If your berries are wildly tart, add another spoon of sugar. If they’re super juicy, add a smidge more cornstarch.
Prep the lattice. Roll the chilled dough between two sheets of lightly floured parchment to about 3 mm thick. Slice into strips roughly 1 to 1.5 cm wide. If you don’t own a rolling pin, a clean wine bottle does the trick.
Assemble. Scatter the berry filling evenly over the warm base, juices and all. Weave the strips on top in a simple over under pattern. It doesn’t need to be perfect; rustic is the vibe. Brush the lattice with milk or the beaten egg, then sprinkle with coarse sugar.
Bake for 35 to 45 minutes, until the top is golden and the berries are bubbling vigorously in the center. If the top browns super fast, tent loosely with foil. Let it cool in the pan for at least 1 hour, preferably 2, so it sets. I think this tastes better the next day, but also, I rarely make it that far.
Lift the bars out by the parchment overhang and slice into 16 to 24 squares. Or just, you know, nibble at the edges like a gremlin. Up to you.

Little notes I wish I knew sooner

If using frozen berries, toss with cornstarch while still mostly frozen, then let them sit 5 minutes so the starch hydrates. Less risk of soupy bars.
Don’t skip the par bake. I once tried rushing this step and regretted it because the base turned soft as a soggy napkin.
Egg wash makes the lattice shiny, milk makes it tender. Water works in a pinch. I learned that the time I cracked the last egg on the floor and watched it slide under the fridge, farewell friend.
Once I used powered sugar in the crust by accident and it was a bit too tender for slicing. Tasted great, just messy.

Variations I’ve tinkered with

Blueberry plus peach: 3 cups blueberries, 2 cups chopped peaches. Add a touch more cornstarch.
Almond twist: Swap 1/2 cup flour for almond flour and add 1/2 teaspoon almond extract. The aroma is next level.
Lemon poppy: Stir 1 tablespoon poppy seeds into the dough and use extra lemon zest. Looks speckled and cute.
One that flopped: I tried honey instead of sugar in the filling once. It tasted lovely but leaked like a sieve, so maybe save honey for drizzling after baking.

Gear I actually use, and workarounds

9 x 13 inch metal pan. Glass runs hot and can overbrown the edges, but it works, just keep an eye.
Pastry blender. Essential for me on fussy days, although a fork or your fingertips does fine if you’re feeling chill.
Rolling pin, or a wine bottle. No judgment. A tall drinking glass works too in a pinch.
Parchment paper for the sling. Foil is okay, lightly butter it so nothing sticks.

Storage and what really happens at my place

Room temp: covered, 1 day. Fridge: up to 4 days. Freeze: wrap tightly and freeze up to 2 months. Rewarm at 300 F for 10 minutes to perk up the crust. Though honestly, in my house it never lasts more than a day.

How we like to serve it

Warm with vanilla ice cream is the classic. A dollop of tangy Greek yogurt in the morning makes it breakfast, no one can convince me otherwise. My dad loves a wee drizzle of cream and a cup of strong tea. When friends drop by, I cut smaller squares so we can all have seconds without pretending we will not.

Pro tips, learned the crunchy way

Chill the lattice strips for 5 minutes if they get soft. I once tried to rush the weave and it tore, then I had to patch it like a wonky quilt.
Wait for visible bubbling in the center before pulling it out. That’s the sign the starch has activated and set the juices. No bubbles, no set.
Let the bars cool long enough to slice. I know, it’s cruel. But cutting too soon turns it into a delicious pile rather than tidy bars.
Taste your berries. Sweet fruit needs less sugar. Sour fruit needs more. Sounds obvious, but I forget and then wonder why it’s a bit puckery.

FAQ because you asked

Can I use frozen blueberries
Yes. Use them form the freezer, don’t thaw fully. Add an extra teaspoon of cornstarch if they’re very icy.

Can I make this gluten free
Probably. I’ve had good luck with a cup for cup style blend. The dough is a touch more delicate, so chill it a bit longer before weaving the lattice.

Do I have to do the lattice
Nope. You can crumble the reserved dough on top like a streusel. It’s quicker and still looks lovely. But if you want to try the weave, this lattice tutorial helped me a ton: see the step by step photos I like.

What thickener is best
I tend to think cornstarch is the simplest, tapioca gives a clearer gel. If you’re curious, this cornstarch vs tapioca rundown is great reading: a practical guide I trust.

Different pan size
You can bake in a 23 cm square pan for thicker bars, add a few minutes to the bake. For conversions, I peek at this pan size guide: super handy reference.

Can I cut the sugar
Sure. Drop the sugar in the filling by a few tablespoons, but don’t skimp in the crust too much or it loses tenderness. Balance is the name of the game.

How do I stop a soggy bottom
Par bake the base, bake until the center bubbles, and cool before slicing. Also, avoid overloading with liquid if your berries are super juicy.

A tiny side note that doesn’t really fit anywhere

I once lost my favorite teaspoon measure for a month. Found it inside the flour bin like a pirate treasure. So if you ever taste a bit more zest in my bars than expected, you now know why I eyeballed for a while.

Quick recap for the distracted baker

Mix dough, press most in pan, par bake. Toss berries with lemon and cornstarch. Roll and slice strips, weave. Bake till golden and bubbly. Cool, slice, share. Easy as blueberry pie bars.