Ingredients
For the Cookie Cake
¾ cup (170g) unsalted butter, softened
¾ cup (150g) granulated sugar
1 large egg
1 teaspoon vanilla extract
½ teaspoon baking soda
½ teaspoon salt
½ teaspoon cream of tartar
2 cups (248g) all-purpose flour
1 cup (220g) M&Ms (spring colors suggested)
½ cup (78g) Easter sprinkles
For the Frosting
3 tablespoons (42g) unsalted butter, softened
1 ½ cups (170g) powdered sugar
1 teaspoon vanilla extract
⅛ teaspoon salt
2 tablespoons (15ml) heavy whipping cream or milk
These ingredients mirror other sugar cookie cake and M&M cookie cake recipes, which use a butter-and-sugar base, egg, vanilla, flour, baking soda, cream of tartar, and plenty of mix-ins. Cream of tartar shows up in many classic sugar cookie formulas to keep the crumb soft and slightly tangy while working with baking soda to provide lift.
Step-by-step instructions
To prepare the pan, heat the oven to 350°F (175°C). Line a 9‑inch round cake pan with foil or parchment, pressing it smoothly into the edges, and coat with nonstick spray. Using a lined, greased pan is standard in cookie cake recipes to prevent sticking and to make lifting the cooled cookie cake easier.
For the cookie cake base, beat the softened butter and granulated sugar together in a large bowl until the mixture looks creamy and well combined. Add the egg and vanilla extract and mix until smooth and slightly lighter in color, similar to how sugar cookie and cookie cake recipes build a fluffy butter-sugar base.
In a separate bowl, whisk together the baking soda, salt, cream of tartar, and flour to break up any clumps and evenly distribute the leavening. Gradually add this dry mixture to the wet ingredients, mixing just until the dough comes together and no dry streaks remain; overmixing can make sugar cookie cakes denser and less tender. Fold in the M&Ms and sprinkles gently by hand so the candies don’t break apart and the mix-ins stay evenly distributed, a common tip in M&M cookie cake recipes.
Press the dough evenly into the prepared pan, smoothing the top with your hands or a spatula so it reaches all the edges. Add a few extra M&Ms on top if you want a more colorful finish, which many cookie cake recipes suggest so the candies are visible after baking.
Bake the cookie cake for about 19–22 minutes, or until the edges turn lightly golden and the center looks just slightly underbaked; it will continue to set as it cools, ensuring a soft, chewy texture rather than a dry one. Let the cookie cake cool completely in the pan on a rack before frosting so the icing does not melt or slide off.
To make the frosting, beat the softened butter until smooth, then gradually add the powdered sugar and mix until the mixture looks thick and a bit crumbly. Add the vanilla extract and salt, then mix in about 1 teaspoon of the cream or milk. Beat until smooth and creamy, adding the remaining cream as needed to reach a soft, spreadable or pipeable consistency similar to buttercream used on sugar cookie cakes.
Transfer the frosting to a piping bag fitted with a 1M tip (or use a zip-top bag with the corner snipped off). Pipe decorative swirls or a border around the cooled cookie cake, then finish with extra sprinkles and M&Ms over the frosting as desired. Slice into 10–12 wedges for serving.