Make the Cupcake Batter: Whisk the flour, baking powder, and salt in a medium bowl. In a large bowl, beat the butter and sugar until fluffy. Add the eggs one at a time, mixing well after each. Stir in the vanilla. Gradually mix in the dry ingredients, alternating with the milk. Start and end with the flour mixture, and mix until just combined—don’t overmix!
Bake the Cupcakes: Fill cupcake liners about ¾ full. Bake at 350°F (175°C) for 18–20 minutes or until a toothpick inserted in the center comes out clean. Let them cool in the pan for 5 minutes, then transfer to a wire rack.
Make the Buttercream Frosting: Beat the butter until creamy. Gradually mix in the powdered sugar. Add the vanilla and heavy cream, beating until light and fluffy. Adjust consistency if needed—add more cream if too thick, or more powdered sugar if too thin.
Decorate the Cupcake: Pipe frosting onto the cooled cupcakes. For bunny ears, cut large marshmallows diagonally and dip the sticky sides into pink sanding sugar. Place them on top, then add pastel sprinkles for a festive touch.