Step 1Heat the oven to 325 degrees.
Step 2In a medium bowl, sift together the flour, baking powder and salt and set aside.
Step 3In a large bowl, stir the brown sugar into the melted butter. Stir in the egg, then the vanilla.
Step 4Stir in the dry ingredients, then fold in the nuts.
Step 5Place the batter in a greased 8-inch square baking pan and bake until set (a toothpick inserted will have moist crumbs), 25 to 30 minutes.
Step 6Cool slightly before serving.