Preheat your oven to 325°F (162°C) and prepare a mini muffin pan with cooking spray.

Combine the cake mix, flour, melted butter, egg, egg yolk, and vanilla in a mixing bowl, mixing until a thick dough forms.

Scoop out the dough with a tablespoon, roll into balls, roll in sugar, and place in muffin cups.

Bake for 14 minutes until puffy but not golden brown.

Create an indent in each cookie using a spoon handle after baking.

Cool dough in the muffin pan for 5-10 minutes before transferring to a wire rack.

Prepare ganache by combining white chocolate chips and heavy cream in a bowl and microwaving until melted and smooth.

Fill each cooled cookie cup with ganache and top with M&Ms to create bunny faces.

Let the filled cups sit at room temperature for about 2 hours to set the ganache.