First, preheat the oven to 190 degrees and prepare a baking sheet. We cover it with baking paper and grease it with oil. Now we proceed to the preparation of the cream. Cooking milk syrup: mix 90 grams of sugar and 3/4 milk and bring to a boil, stirring constantly. Mix the starch with the remaining milk and add to the boiling milk syrup. Make a smaller fire and stir until thickened. Here is the consistency obtained. Cool to room temperature. When cooled, it becomes jelly-like. Sift and mix flour and 15 grams of cocoa. Beat eggs with sugar until such a foam. In the beaten eggs, add the flour with cocoa. Knead the dough. We spread the dough on a baking sheet and put in the oven for 15 minutes. Meanwhile, whisk 90 grams of butter until white, gradually adding our jelly-like milk syrup. Add cognac and the remaining cocoa. Do not forget about our biscuit, check with a toothpick for readiness, take it out and put the cake on a clean, dry towel. My baking paper peeled off very easily. We turn the cake together with a towel into the roll and wait until it cools. When it cools down, unfold our biscuit, grease it with cream and turn it again. We wrap it in cling film and send it to the refrigerator. 30 grams of butter with 50 grams of chocolate put on a small fire and stir until completely dissolved. Lubricate our roll with icing and put it in the refrigerator again. It is advisable to keep the roll in the refrigerator for 24 hours before serving.