Ingredients
For the Shortbread Crust
- 1 1/2 cups (342 grams) soft unsalted butter (I recommend a high-quality brand)
- 3/4 cup (150 grams) brown sugar
- 3 1/4 cups (415 grams) all-purpose flour
- 1/2 tsp. salt
- 2 teaspoons vanilla extract
For the Blueberry Filling
- 3 cups blueberries, fresh or frozen
- 1/2 cup (100 grams) granulated sugar
- 3 tablespoons (24 grams) cornstarch
- Zest of 1 lemon
- Juice of two lemons, about 6 tablespoons
Instructions
In a pan, stir the sugar and cornstarch together. Add in the blueberries, lemon zest, and lemon juice and stir them to coat in the sugar mixture.
Place the pan over medium-low heat and cook, stirring frequently. As they cook, the blueberries will burst, releasing their juices. If the mixture seems dry, mash a few of the blueberries to make it juicier.
Continue cooking for 6-8 minutes, or until the mixture is thickened and has a jam-like consistency. The juice should look translucent and not cloudy–if it is, the cornstarch hasn’t cooked out completely and the jam will have a pasty consistency.
Set it aside. The filling will get thicker as it cools.
Line a 9″x9″ baking pan with parchment paper. Preheat the oven to 350F and set out the butter to soften to room temperature. It should be soft and have a dent when you press on it, but not be oily.
In a mixing bowl, rub the lemon zest into the brown sugar. Add the soft butter and cream it together with a hand mixer until it’s fluffy and light. This should take about 2-3 minutes.
Add the salt, flour, and vanilla to the butter and sugar. Mix until all of the flour is combined completely.
Press 2/3 of all the dough into the bottom of the parchment lined pan.
Spread the cooled jam in the pan. Crumble the remaining the 1/3 of the dough over the top of the jam.
Place the pan in the oven and bake for 45-50 minutes, or until the top is golden brown and no longer looks doughy.
After baking, remove the bars from the oven and allow them to set and cool. Cut into bars.