baking powder together into a large bowl. Cut in the butter and add the 4 beaten eggs, blending well. Then add the nuts. Grease a cookie sheet and spread the batter into two rectangular shapes, about 1/2-inch thick. Brush the tops with the remaining beaten egg. Bake in a preheated 350 Degree F. oven for about 45 minutes or until the tops are brown. Cut into biscotti (3/4-inch slices) and turn each slice on its side on the cookie sheet. Turn the oven down to 325 Degrees F. and return the cookie sheet to the oven to let the slices toast for about 10 minutes. Turn the biscotti over and toast the other side, watching closely so they don't get too brown.