1 1/2 sticks of unsalted butter
1 1/2 c. light brown sugar
1 large egg plus 1 egg yolk, at room temperature
2 t. vanilla extract
1/2 t. salt
1/4 t. baking powder
1 1/2 c. all-purpose flour
chocolate chips to taste
flaky sea salt
Preheat the oven to 350 degrees. Spray an 8x8 pan with nonstick spray.
Melt the butter. Add the sugar to the hot butter and whisk to combine. Cool until warm.
Add the egg, egg yolk, and vanilla and whisk until smooth.
Stir in the salt, baking powder, and flour with a wooden spoon.
Gently stir in chocolate chips or other mix-ins to taste.
Place the batter into the prepared pan and top with additional chocolate chips, if desired.
Bake for approximately 25 minutes until the edges are lightly golden but the center is slightly jiggly. Bake until the edges are golden brown (approx. 30 minutes) if you want a firmer square.
Sprinkle with flaky sea salt and cool on a wire rack before cutting.