Beat egg yolks and whites separately until whites are stiff. Combine and, still
beating, slowly add sugar, flour and butter.
Place wax paper on a baking sheet.
Butter the wax paper. Spread dough 1/2-inch thick over the wax paper.
Bake for 50 minutes to 1 hour.
When done, remove from the oven and roll up quickly, paper and all. Let rest
for 15 to 20 minutes.
Unwrap, carefully loosening paper, but leaving it under the cake. Spread cake
with jam. Re-roll, discarding the wax paper. Roll entire cake in confectioners'
sugar. Cut off both ends for a neat appearance.