Preheat the oven to 350°F (175°C). Grease the cupcake pan.

In a mixing bowl, cream together the butter and sugar until light and fluffy.

Add eggs one at a time, mixing well after each addition. Stir in vanilla.

In another bowl, whisk together flour, baking powder, and salt. Gradually add to the creamed mixture, alternating with milk.

Fill the cupcake pan with batter, about 2/3 full. Bake for 20-25 minutes or until a toothpick comes out clean.

Let the cupcakes cool in the pan for 10 minutes, then transfer to a cooling rack.

In a mixing bowl, beat the softened butter until creamy. Gradually add powdered sugar, vanilla, and milk, beating until smooth.

Once the cupcakes are completely cool, frost the tops generously with the buttercream frosting.

Stack the frosted cupcakes in a circular pattern to form a cake shape.

Top with sprinkles for decoration.