Make the Cake:

1. Preheat the oven: Preheat your oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper and lightly grease it.
2. Mix dry ingredients: In a medium bowl, whisk together the flour, baking powder, and salt.
3. Cream butter and sugar: In a large bowl, use a hand or stand mixer to beat the butter and sugar until light and fluffy (about 2–3 minutes).
4. Add eggs and vanilla: Beat in the eggs one at a time, followed by the vanilla extract.
5. Combine wet and dry ingredients: Gradually add the dry ingredients to the wet mixture, alternating with the milk, starting and ending with the dry ingredients. Mix until just combined.
6. Color the batter: Stir in a few drops of red or pink gel food coloring until the desired shade is achieved.
7. Bake: Pour the batter into the prepared pan and spread it evenly. Bake for 20–25 minutes, or until a toothpick inserted into the center comes out clean. Let cool completely before cutting.

Make the Frosting:
8. Cream the butter: In a large bowl, beat the softened butter until creamy. Gradually add powdered sugar, 1 cup at a time, beating well after each addition.
9. Adjust consistency: Add heavy cream or milk, 1 tablespoon at a time, until the frosting reaches your desired consistency. Mix in vanilla extract and food coloring if using.

Assemble the Mini Cakes:
10. Cut shapes: Use a heart-shaped cookie cutter to cut out cake pieces from the cooled cake. You’ll need 2–3 hearts per mini cake, depending on the desired height.
11. Layer with frosting: Spread a layer of frosting on one heart-shaped piece, then stack another piece on top. Repeat until you have stacked layers.
12. Decorate: Frost the outside of the mini cakes if desired, and decorate with sprinkles, candies, or edible glitter.