Make the Cake:

1. Preheat oven to 350°F (175°C). Grease and line a 9×13-inch baking pan with parchment paper.
2. In a bowl, whisk together flour, baking powder, baking soda, and salt (add cocoa powder for red velvet).
3. In a separate bowl, beat butter and sugar until light and fluffy.
4. Add eggs, one at a time, mixing well after each. Stir in vanilla extract (and vinegar + red food coloring for red velvet).
5. Alternate adding the dry ingredients and buttermilk, mixing until just combined.
6. Pour batter into the prepared pan and smooth the top.
7. Bake for 18-22 minutes, or until a toothpick inserted in the center comes out clean.
8. Let cool completely before cutting.

Cut & Assemble the Mini Cakes:

9. Use a heart-shaped cookie cutter to cut out mini cakes from the cooled sheet cake.
10. If making layered cakes, spread frosting or glaze on one cake and stack another on top.

Make the Glaze or Frosting:

11. For the glaze, whisk together powdered sugar, milk, and vanilla until smooth. Add a drop of food coloring if desired.
12. For buttercream, beat butter, powdered sugar, milk, and vanilla until light and fluffy. Tint with food coloring if desired.

Decorate & Serve:

13. Drizzle the glaze over cakes or pipe buttercream on top.
14. Decorate with sprinkles, chocolate chips, or fruit.
15. Let set for 15 minutes, then serve!