In a large saucepan, combine the first 5 ingredients. Bring to a boil. Reduce heat. Simmer, uncovered, until sauce begins to thicken, 12-15 minutes; set aside.
In a large bowl, combine the flour, baking powder, sugar and salt. Combine egg yolks, milk and butter; stir into dry ingredients just until combined. Stir in pineapple, coconut and nuts. Beat egg whites until stiff peaks form; fold into batter (batter will be thick).
Preheat waffle maker. Fill and bake according to manufacturer's directions. Serve with pineapple sauce and additional nuts if desired.