Preheat oven to 350 degrees.

Separate egg yolks and whites, keeping whites at room temperature.

In bowl of an electric mixer, cream sugar and butter together until pale yellow and fluffy.

Add egg yolks and beat until fluffy again, 2 to 3 minutes on medium-high speed.

In a separate bowl combine flour and baking powder.

In a third bowl mix milk and vanilla.

Alternately add the flour mixture and the milk mixture to the butter mixture (a fourth at a time) until all are combined.

Beat until smooth after each addition.

Beat egg whites with cream of tartar until soft peaks form and, using a large spatula, gently but thoroughly fold into flour-and-butter mixture.

Grease bottom of a 9- by 13-inch metal baking pan.

Pour in batter and bake for approximately 25 minutes, until golden brown. Allow to cool.

Stir the three milks together thoroughly; do not beat.

Whip cream and sugar together until stiff for icing.

When cake is cool, slice or peel off the thin top crust.

Ice sides first, creating a small lip on top to catch milk mixture.

Pour milk mixture evenly over top of cake. Poke holes if necessary to facilitate soaking.

Finish icing top.

Refrigerate.