Preheat oven to 350 degrees F (175 degrees C). Grease a 9x9 inch baking pan.
To prepare Pastry: In a large bowl, mix the eggs and both sugars together. Blend in the nuts and sift the flour with the baking powder and salt. Add to egg mixture and blend well. Press into the bottom of the greased pan.
Bake for 20 to 25 minutes. While pastry bakes, mix 1/4 cup of brown sugar, cream and cashews into the melted butter.
Spread over baked pastry and place under a broiler for about 1 minute, until topping bubbles and becomes brown. Cut into bars while warm. Let cool in pan.