Heavily butter an 8-inch square pan. Heat oven to 250 degrees F.
Beat whites until very stiff. Beat cream stiff, then add sugar to it a little
at a time, folding it in until all the sugar is used. Fold whites into the cream
mixture by the large spoonful, very carefully, alternating with spoonsful of the
flour and the vanilla extract. Work as lightly and as gently as you can. Pour mixture
into the buttered pan and bake for 1 1/2 hours or until it is pale golden on top.
At the end of the baking time, open the door carefully and look. If it is golden,
test with a thin sharp knife. If the knife comes out clean, the cake is done.
When the cake is done, turn the oven off, close door very gently, and let the
cake cool in the oven.
When cold, cut it into ladyfinger strips to serve. The bottom is jelly-like and
the top is like meringue.