For the cherry crumble cake, cream butter and sugar until fluffy. Add eggs and continue to beat. Mix flour, cornstarch and baking powder and sift into the mixture. Mix everything together, adding milk slowly until the dough falls heavily from the spoon.
Pour the batter into a shallow silicone mold and smooth it out. Spread the drained cherries on top and drizzle with the chocolate liqueur.
Knead the ingredients for the crumble into even crumbles and spread on the cake. Bake at 150 degrees for 30-40 minutes (test with a wooden stick).