Ingredients

2 cups all-purpose flour

1 cup old-fashioned rolled oats

3/4 cup unsalted butter, cold and cubed

3/4 cup brown sugar

1/4 cup granulated sugar

Zest of 2 lemons (for crumble)

1/2 teaspoon baking powder

1/2 teaspoon salt

1 can (14 oz) sweetened condensed milk

1/3 cup freshly squeezed lemon juice

Zest of 1 lemon (for filling)

2 large egg yolks

1 teaspoon vanilla extract

2 cups fresh or frozen blueberries

1 tablespoon cornstarch

2 tablespoons granulated sugar (for berries)

Instructions

Step 1: Preheat your oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper, leaving an overhang for easy removal.

Step 2: In a large bowl, combine flour, oats, brown sugar, granulated sugar, baking powder, salt, and zest of 2 lemons.

Step 3: Add cold, cubed butter and cut it into the dry ingredients using a pastry cutter, fork, or your fingers until the mixture resembles coarse crumbs. Reserve 1 heaping cup of this mixture for the topping.

Step 4: Press the remaining crumble mixture firmly and evenly into the bottom of the prepared pan. Bake for 10 minutes, then remove and let cool slightly.

Step 5: In a medium bowl, toss blueberries with cornstarch and 2 tablespoons granulated sugar. Set aside (do not thaw if using frozen).

Step 6: In another bowl, whisk together sweetened condensed milk, lemon juice, zest of 1 lemon, egg yolks, and vanilla extract until smooth.

Step 7: Pour the lemon cream filling over the baked base and spread evenly.

Step 8: Spoon the blueberry mixture evenly over the lemon layer.

Step 9: Sprinkle the reserved crumble mixture over the top.

Step 10: Bake for 35–40 minutes, or until the top is golden brown and the filling is just set. If the top browns too quickly, cover loosely with foil for the last 10 minutes.

Step 11: Let the bars cool completely in the pan (at least 2 hours). For clean slices, chill in the refrigerator for 1 hour after cooling.

Step 12: Lift the bars out using the parchment overhang and cut into 12–16 squares.

Tips & Variations

Use fresh lemons for the brightest flavor, but bottled lemon juice can work in a pinch.

For a nutty twist, mix 1/2 cup chopped almonds or walnuts into the crumble.

Swap blueberries for raspberries or blackberries to change up the fruit flavor.

Allow the bars to chill thoroughly before slicing to prevent them from falling apart.

FAQs

Can I use frozen blueberries without thawing?

Yes, use frozen blueberries directly and toss them with cornstarch and sugar as instructed. This helps prevent excess moisture and keeps the bars from becoming soggy.

How do I get clean slices when cutting the bars?

Cooling the bars completely and chilling them in the refrigerator for at least an hour before slicing makes it easier to cut clean squares. Use a sharp knife and wipe it clean between cuts.