Begin by creaming together 1 cup of unsalted butter and 1 ½ cups of granulated sugar until light and fluffy, about 2-3 minutes. Add in 1 egg and 1 teaspoon of vanilla extract, mixing until smoothly combined. Gradually incorporate 3 cups of all-purpose flour and 1 teaspoon of baking powder, stirring until a soft dough forms.

Transfer the dough to a lightly floured surface. Roll out the dough to approximately ¼ inch thickness using a rolling pin. Cut out heart shapes with a cookie cutter and place on a parchment-lined baking sheet.

Preheat your oven to 350°F (175°C). Bake the cookies for 8-10 minutes, or until lightly golden. Cool on a wire rack.

While cookies cool, make the buttercream. Beat 1 cup of softened unsalted butter until creamy, gradually add 4 cups of powdered sugar, mixing on low until incorporated. Blend in 2 tablespoons of milk and 1 teaspoon of vanilla extract.

Choose two heart-shaped cookies for your layers. Spread a layer of buttercream on top of one cookie, then place the second cookie on top and frost the top and sides evenly.

Decorate with your favorite toppings such as fresh berries, edible flowers, and colorful sprinkles to enhance the festive look.

Allow the cake to set at room temperature for about 30 minutes before serving.