Funfetti Cake Mix Sandwich Cookies are simply made with a boxed cake mix, then filled with buttercream frosting. Perfect for birthdays, parties and celebrations!
In a small bowl, mix the cake mix, egg, cream cheese and butter until it is all well combined. Roll the dough into 1-inch balls. This makes about 44 balls.
Roll the balls in sprinkles, then place them on a cookie sheet. Gently press down on the top of the balls to slightly flatten them.
Bake at 350 degrees for 10 minutes. Move the cookies to a wire rack to cool.
In a stand mixer bowl, with the mixer on medium speed, whip the butter for 2-3 minutes until it is almost white in color.
Add in the powdered sugar, vanilla and 1 1/2 tablespoons milk. Add a drop of food coloring, if desired. Beat on low speed for 3-5 minutes, adding in another 1/2 tablespoon of milk if the buttercream needs to be thinner.
Spread or pipe frosting on half of the cookie. Place another cookie on top of the frosting to make sandwiches. Store in an airtight container.