Step 1

Preheat oven to 350°F. Line an 8-inch square baking pan with a parchment paper sling. Then butter or spray the baking dish with nonstick cooking spray.

Step 2

In a medium bowl mix together the all purpose flour, baking powder and salt. Set aside.

Step 3

In a large mixing bowl, combine together the melted butter and brown sugar. Stir in egg and vanilla.

Step 4

Combine flour mixture to the brown sugar mixture a little at a time, mixing between additions. Mix in chopped walnuts. The batter will be very thick.

Step 5

Pour the brownie batter in the prepared pan. Place on the center rack of the oven and cook for 20-25 minutes until a toothpick inserted in the center comes out clean. Leave the blondies in the pan to cool on a wire rack. Let cool completely before frosting.

Step 6

Make the frosting by heating butter in a light colored small saucepan over medium heat. Stir continuously for about 6-8 minutes until a light golden brown, then remove from heat. Immediately pour into a heat safe container like a liquid measuring cup. If left in the pan the butter will burn.

Step 7

To the bowl of a stand mixer, add in the powdered sugar and brown butter. Next, mix in the half and half and the vanilla extract. Blend until smooth. Frost blondies once they are completely cooled.

Step 8

Make the chocolate layer by melting the chocolate squares in a small saucepan with the butter over low heat. Stir constantly. Once slightly cooled, pour over the frosting layer of the blondies. Tip the pan around to fully cover the top.