Heat oven to 350˚ F. Grease and flour a 9” x 13” pan.
In a clean, dry, large bowl, beat egg whites until soft peaks form when beater is lifted. Set aside.
With mixer on medium speed beat butter until softened and light in color, about 3 minutes. Add sugar and continue to beat until very light, scraping down sides. Turn mixer to low and mix in coffee until completely combined.
In a medium bowl, combine flours and baking powder. Stir dry ingredients into batter being careful not to overmix.
Gently stir a quarter of the egg whites into batter. Folder the remaining egg whites into the batter.
Pour in to prepared baking dish. Bake for 20 minutes until the cake springs back lightly. Cool for 15 minutes and remove from pan onto a wire cooling rack. When completely cool, cut into 24 squares.
To make frosting, with mixer on medium speed, beat butter until softened and light in color, about 3 minutes. Lower speed and add cream, mixing to incorporate completely. On lowest speed, add powdered sugar, beat until smooth and creamy.
Frost all sides of cakes and roll in chopped peanuts.