Preheat oven to 350 degrees.
Stir together baking powder, soda, salt, and flour. Sift dry ingredients into a medium bowl, stir in 1/4 cup nuts and set aside.
In another, larger, bowl mix 1 cup brown sugar and 5 tablespoons melted butter. Combine well. Add eggs and vanilla and mix well, again.
Stir flour mixture into butter/brown sugar mixture, a little at a time. When well mixed stir in white chocolate chips.