Every game in Roblox is made via the Create tab and comes with a free-to-use app called Roblox Studio. From there, you can use the app to make whatever you want.

How to make ice cream in Grow a Garden? Make ice cream with 1 Strawberry and 1 Corn, or 1 Blueberry and 1 Corn. Add them to the Cooking Pot with E, and cook.