In a large mixing bowl, beat egg yolks and sugar with an electric mixer for 3 to 4 minutes, until thick and lemon colored. Set whites sides in a separate bowl. Wash and dry beaters and keep them handy. Whisk the sour cream, milk, lemon extract and lemon zest into the egg yolk mixture and set aside. Sift the dry ingredients into a bowl and reserve. Using the clean beater, beat the egg whites until they hold soft peaks. Whisk the dry ingredients into the liquid until just smooth. Fold in the egg whites. Cook the pancakes on a preheated greased griddle or skillet for about 1.5 minutes, flip and cook for about 1 minutes on the second side. Serve with warm blueberry sauce and whipped cream.