Melt the butter in a large pot, add the flour quickly and immediately pour in the boiling milk, with the vanilla in it. Add the sugar and stir the cream until it comes to a boil, then remove it from the heat. Divide this mixture into 2 parts.
Add a beaten egg yolk to one, to the other - a second yolk, beaten with the cocoa. Beat the yolks into dense foam, but only the 2, because one always puts more yolks than whites in a soufflé. Distribute the egg white evenly in both mixtures.
Coat small baking forms with butter, pour in 1 part of the cocoa soufflé, and then the yellow soufflé on top. Bake the forms for about 25 minutes in a moderate oven.
Pour on a caramel made from the sugar and 1-2 tablespoons red rum to the finished soufflé and serve.