2/3 cup butter, softened
2 cups packed brown sugar
1 tsp vanilla extract
2 cups all purpose flour
2 tsp. baking powder
1/4 tsp salt
1 cup peeled, cored, and chopped apples
1/2 cup chopped walnuts or pecans
1/2 cup butter
1 cup packed brown sugar
1/4 cup milk
Preheat oven to 350ºF (180ºC). Lightly grease a 13" x 9" baking dish then line with parchment paper, overlapping two sides for easy removal.
In a large bowl, cream butter and brown sugar until smooth. Add the eggs and vanilla and mix well.
Stir in the flour, baking powder, salt, apples and nuts. Stir until thoroughly combined. Spread batter in prepared pan.
Bake for 30 to 35 minutes, or until set and golden. Cool on a wire rack.
To make the frosting, melt butter in a saucepan, then add the brown sugar and milk and bring the mixture to a boil. Remove from heat; let cool and stir in the icing sugar. Spread frosting onto cooled blondies. Cut into 1-inch squares and serve.