Preheat oven to 350°F. Grease and flour two 8-inch pans.
Beat butter and sugar until light. Add eggs one at a time, then vanilla.
Mix flour, baking powder, and salt. Add dry ingredients alternately with milk.
Fold in sprinkles gently so they don’t bleed color.
Divide batter, bake 22–25 minutes. Cool completely.
Beat butter for frosting, add powdered sugar gradually. Thin with milk to spreadable consistency.
Stack layers with a thin coat of buttercream between them. Crumb coat and chill 20 minutes.
Finish with a smooth coat of buttercream. Sprinkle extra sprinkles on top and press edible gold flakes sparingly.