Step 1

Preheat the oven to 375 degrees F. Line an 8x8-inch pan with parchment paper so it overhangs on two sides so the bars are easy to lift out once baked and cooled.

Step 2

Mix together all of the ingredients in a medium bowl except the blueberries. (Add the egg if using.) Stir in the blueberries gently.

Step 3

Press into the prepared pan so the batter is even and pressed to the edges.

Step 4

Bake for 24-26 minutes or until the edges are lightly golden brown and set.

Step 5

Cool fully. (Really, please let it sit until it's cool to the touch! You can pop it into the fridge to speed this up if you'd like. It may crumble a bit if you slice when still warm.)

Step 6

Slice into bars and serve or store. I typically cut into 16 small squares, but you can cut them larger if desired.