1. Preheat oven to 350°F.
2. Cream margarine and sugars. Add yolks and vanilla. Add dry ingredients on slow speed and mix well.
3. Pat into two greased 8×8-inch pans. Sprinkle ﬁlling ingredients on top of dough.
4. In a separate bowl, beat egg whites until soft peaks form; add brown sugar slowly until whites are stiff and glossy.
5. Spread on top of ﬁlling in both pans.
6. Bake at 350°F for 40 minutes.
7. When cool, cut into squares.