First, we want to lighten the batter. Using a rubber spatula, gently mix 1/3 of the egg whites into the batter. This helps to lighten the batter making it easier to work in the remaining egg whites without deflating them. Add half of the remaining egg whites to the batter. With the blade of your spatula, slice straight down through the middle of the egg whites until you hit the bottom of the bowl. Scrape your spatula along the curve of the bowl, gently scooping up the batter and the egg whites. Fold them over on top of the remaining egg whites. Give the bowl a quarter-turn and repeat the process.  Slice straight down through the middle of the egg whites until you hit the bottom of the bowl. Scrape your spatula along the curve of the bowl, gently scooping up the batter and the egg whites. Fold them over on top of the remaining egg whites. Repeat this folding motion until the egg whites have been completely incorporated into the batter. The mixture may still be a bit lumpy and that's ok. If you continue folding until the batter is 100% smooth the egg whites will start to deflate. Add the remaining egg whites and repeat the folding process.