"Blocks of ice cream in every flavor you could think of, apple pies, treacle tarts, chocolate eclairs and jam doughnuts, trifle, strawberries, Jell-O, rice pudding..." (Sorcerer's Stone 125).
Do we really need to go over jello-making? Here we go then: Buy a box of Jell-O. Follow the instructions of the back. Tada! Jell-O.