Heat oven to 350 degrees F. In a large mixing bowl, cream butter and sugars until light and fluffy. Add eggs and vanilla; mix well. Combine the flour, baking powder and salt; add to creamed mixture and mix well. Stir in the white chips, chocolate chips and ½ cup nuts. (Jane note: for the ½ cup that I mixed into the batter, I pulsed the nuts in my Cuisinart processor, so they got chopped up pretty good. I liked how the small bits spread throughout the batter. For the ¼ cup of nuts I sprinkled on top, I hand chopped for a little bit bigger pieces.)
Spoon into a greased 9 x 13 baking pan; spread to evenly cover bottom of pan. Sprinkle with remaining nuts. Bake for 25 to 30 minutes, until top begins to crack and is golden brown. Cool completely on wire rack, then cut into bars. Makes about 2 dozen bars.
Recipe by This Week for Dinner at https://thisweekfordinner.com/chunky-blonde-blondies/