{T}, Sacrifice a creature: Create a Food token. If the sacrificed creature's toughness was 4 or greater, create two Food tokens instead. (They're artifacts with "{2}, {T}, Sacrifice this token: You gain 3 life.")
Food is an artifact type. Even though it appears on some creatures, it's never a creature type.
Whatever you do, don't eat the delicious cards.
You can't sacrifice a Food to pay multiple costs. For example, you can't sacrifice a Food token to activate its own ability and also to activate Maraleaf Rider's ability.
No player may take actions between the time you announce you're activating Witch's Oven's ability and the time you sacrifice a creature. Notably, they can't try to remove or shrink the creature you'd like to bake.