Preheat the oven to 350° F. and grease an 8 x 8 inch baking pan with shortening or butter.
Sift together the flour and baking powder. Remove and reserve ¼ cup to be used with the berries later. Set the rest aside.
In a clean bowl, beat the egg whites together until stiff. In the last minute of beating, add ¼ cup sugar and beat until you get stiff, glossy peaks. Set aside.
Cream shortening with ½ cup of sugar in a stand mixer until light and fluffy. Add the unbeaten egg yolks and vanilla. Combine until the mixture is smooth and creamy.
Alternately, add the remaining 1¼ cups of flour with the milk to the stand mixer set on low speed, beating until all the ingredients are well incorporated.
Toss the berries together with the reserved ¼ cup of the flour mixture.
Using a rubber spatula, fold in the beaten egg whites into the batter and then fold in the blueberry/flour mixture.
Add the batter to the greased 8 x 8 inch baking pan. Sprinkle top of batter lightly with the remaining ¼ cup of sugar.
Bake at 350° F. for 50 to 60 minutes. You can test it with a tooth pick to make sure it's done.
Serve with your favorite ice cream or make some homemade whipped cream.