Preheat & Prep

Start by preheating your oven to 350°F. Grease a 12-inch springform pan with butter. If you don’t have a 12-inch pan, a 10-inch will do—just bake it a tad longer.

Mix the Dough

In a large bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy. Add the eggs one at a time, followed by the vanilla extract. Sift in the flour, baking soda, and salt, then mix until everything comes together into a soft dough. Gently fold in the M&Ms, walnuts, and sprinkles.

Press & Bake

Transfer the dough to your prepared pan and press it evenly across the bottom. Pop it in the oven for 18–20 minutes, or until golden brown around the edges but still slightly soft in the center. Once it’s done, press a few extra M&Ms onto the hot cookie while it’s still warm. Let it cool completely.

Whip Up the Frosting

While the cookie cools, make the frosting. Beat the butter and shortening until smooth and fluffy. Gradually add the powdered sugar, salt, and vanilla extract, mixing until creamy. If it’s too thick, add a splash of milk. Stir in the pink food coloring for that pop of springtime color.

Decorate & Serve

Once the cookie is completely cool, remove it from the pan and transfer it to a serving plate. Pipe the frosting around the edges using a star-tip nozzle, then sprinkle more pastel sprinkles on top. Slice it like a pie, serve, and watch it disappear!