Pipe the frosting onto the cupcakes using a large round piping tip like the Wilton 1A decorating tip.
With an offset spatula, smooth and level out the top of each cupcake. You will need a relatively flat surface to place the cookie cutter on to.
Gently place your heart shaped cookie cutter on top. You don't need to push it down super far—just enough so there are no open gaps between the cookie cutter and the frosting.
Add a small amount of sprinkles inside the cookie cutter using a teaspoon or a small spoon, preferable with a long handle works well.
Rotate and tilt the cupcake around to move the sprinkles into place. This helps to cover any open areas. If you need to add in more sprinkles though, go for it.
When finished, tap the sprinkles gently into place using your finger or food tweezers. If you don't get all the sprinkles, the next step will help remove them!
Remove any excess sprinkles by simply placing a finger on top of the cookie cutter and carefully tilting it over top of the bowl.
To remove the cookie cutter, gently lift the cookie cutter up and away from the cupcake using both hands. With your finger or the food tweezers, you can pat down any remaining loose sprinkles.
Repeat again until all of your cupcakes are decorated, then enjoy!