Can you premake wontons and cook next day?

Yes but they need to be covered well with plastic wrap so they don't dry out. Even better I make a ton (haha) and freeze them untouching on parchment paper on a baking sheet. Then I just store them in a zip lock bag. Easy to take out as many as needed for a meal and they don't need to be defrosted before boiling (boil them a minute or two longer if frozen)