To take a round baking-pan of 20 centimeters of diameter and to cover it with some greasy oven paper. To take a bowl and to mix, sieving together, flour and yeast. With a wood spoon to unite and to mix, for 2-3 minutes, the butter, the sugar, the margarine and the eggs. To divide the pasta that is gotten in 2 parts. To let boil 3 spoons of water and to mix with the cocoa; to pour the all in one of the two bowls. To mix emphatically. To prepare pasta in the baking-pan taking alternatively a spoon of normal pasta and one of that to the chocolate. To level slightly and, with the help of a skewer, to realize the effect of the marble. To bake and to cook for 50-55 minutes. The cake has to become elastic, gilded and swollen. After the cooking, with a spatula, to detach the cake from the baking-pan and to remove the paper. To this point to let cool completely.