Using six 4-oz ramekins or oven-safe glass bowls, fill each almost to the top. (Adjust accordingly if your ramekins are a different size.)
Blend the butter and the sugar in a bowl. Add the egg and beat together until creamy.
*For an egg-free version, use 3 Tbsp aquafaba to replace one egg.
If you can’t eat it all in one sitting, or if you want to make them for a future day, they freeze well. Keep them in an airtight container in the freezer. Thaw before serving. Pop them in the microwave if you want to warm them.
Recipe adapted from Fifteen Spatulas