Step 1

1 Preheat the oven to 350 degrees

Step 2

2 Use a little butter to grease an 8-inch square baking pan

Step 3

3 Melt the 8 tablespoons of butter in a small saucepan over medium heat

Step 4

4 It will foam; continue to cook until the melted liquid smells nutty and turns brown

Step 5

5 Watch closely to avoid burning or scorching, and reduce the heat as needed

Step 6

6 Pour through a fine-mesh strainer into a heatproof bowl; let cool

Step 7

7 Whisk together the flour, baking powder and salt in a medium bowl

Step 8

8 Add the brown sugar to the cooled brown butter, whisking until smooth, then add the egg and vanilla extract

Step 9

9 Whisk until well incorporated

Step 10

10 Stir in the flour mixture to form a smooth, soft dough

Step 11

11 Transfer to the baking pan and smooth into an even layer

Step 12

12 Bake (middle rack) for 20 to 25 minutes, or until a toothpick inserted into the center comes out clean

Step 13

13 Cool for 15 minutes before cutting into 12 equal pieces