As the title "Only 4 Ingredients" suggests, this is a recipe for chewy "butter mochi" that uses only six ingredients: mochi rice cakes, water, sugar, butter, egg yolk, and potato starch, and is cooked using only a microwave and refrigerator. Cut the mochi rice cakes into small pieces and heat them in the microwave with water, then mix until smooth. After that, add the sugar, butter, and egg yolk and mix well. Spread the mixture into a container dusted with potato starch and chill in the refrigerator for at least 3 hours until firm. Once chilled and firm, cut into your desired size and it's ready. Perfect as a snack or gift, and recommended for beginners. The key is to mix without leaving any lumps.