Blueberry Puffs

Divide berries into 6 buttered large custard cups. Cream butter and sugar and the until light. Add egg yolk and vanilla, and beat well. Sift dry ingredients, add alternately with milk to first mixture beating until smooth. Fold in stiffly beaten egg white. Spoon batter over berries. Bake in moderate oven at 325°F for about 30 minutes. Serve with whipped cream.