Preheat your oven to 350°F (175°C). Grease three 8-inch round cake pans with butter or cooking spray and line with parchment paper.

In a stand mixer, combine 2 cups flour, 1.5 cups sugar, 2.5 teaspoons baking powder, and 0.5 teaspoon salt. Mix on low speed, then gradually add 0.5 cup of butter until the mixture resembles moist sand.

In a separate bowl, whisk together 1 cup milk, 3 eggs, 0.5 cup vegetable oil, and 2 teaspoons vanilla extract until combined.

Slowly pour the wet mixture into the dry ingredients while mixing on low speed. Stir until just combined.

Divide the batter among the prepared pans and bake for 22-25 minutes until golden brown. Cool in the pans for 10 minutes.

Turn the cakes out onto a wire rack and allow them to cool completely.

In a mixing bowl, beat 1 cup butter until smooth, then gradually add 4 cups powdered sugar, 0.25 cup heavy cream, and 1 teaspoon vanilla. Whip until fluffy.

Assemble the cake by stacking layers with frosting in between and covering the top and sides with frosting.

Decorate with Peeps and let the cake sit at room temperature for 30 minutes before slicing.