In a medium mixing bowl stir together flour, sugar, baking powder, and salt. Make a well in the center of mixture; set aside.
In another medium mixing bowl beat egg yolks slightly. Stir in milk, shortening, chocolate, and vanilla. Add chocolate mixture all at once to flour mixture. Stir until just moistened (batter should be lumpy). Stir in nuts.
In a small mixing bowl beat egg whites until stiff peaks form (tips stand straight). Gently fold beaten egg whites into flour and chocolate mixture, leaving a few fluffs of egg white. Do not overmix.
Pour 1 to 1-1/4 cups batter onto grids of a preheated, lightly greased waffle baker. Close lid quickly; do not open until done. Bake according to manufacturers directions. When done, use a fork to lift waffle off grid. Repeat with remaining batter. If desired, serve warm with whipped cream. Makes twelve to sixteen 4-inch waffles.