Crumble the yeast into the cream and mix with a pinch of sugar and flour. Cover and let rest in a warm place for 5 - 10 minutes.
Put the sugar, flour, salt, melted and cooled margarine and the egg yolks in a mixing bowl, then add the yeast - cream. Mix everything together and knead or beat vigorously until the dough loosens from the bowl and fingers. Cover with foil and let rise to double size in a warm place (takes about 20 minutes).
Then knead again and divide the dough into three parts. Roll each out into a round, 0.5 cm thick sheet of dough. Rub out or cut out 15 triangles with a pastry wheel or knife. From the broad edge to the tip, roll it up loosely into croissants and place on a greased tray. Let the croissants rise briefly again.
Bake in a preheated oven at 200 ° C for about 10 minutes.