In a bowl, crumble the leftover cake, add whipping cream, vanilla extract, and sugar to form the dough. This should not be too wet. So depending on how moist or dry your cake is, add the cream or milk little by little at a time. The dough should be such that it is easy to roll bite size balls out of it.
2 cups Leftover cake, 4 to 5 tablespoon Heavy whipping cream, ¼ teaspoon Vanilla extract, ½ teaspoon Sugar