Line a baking sheet (I used a 10x15-inch sheet) with parchment paper. For thicker hearts, use a smaller baking dish. Set aside.
Add heavy cream to a mixing bowl. Start mixing at the lowest speed, and then gradually increase speed to medium until the cream starts to get thicker. (The gradual progression prevents you from spraying yourself with cream.)
When the cream starts to thicken, stop the mixer. Slowly add in the confectioners' sugar and then resume mixing again, starting with low speed and increasing to medium speed and eventually moving to a high speed.
The cream will thicken and start to peak. Mix on high until the cream is thick and stiff. This happens quickly, (the stage between soft and stiff peaks), so watch it closely.
Fold in food coloring (if using).
Gently fold in 1/4 cup of water (to aid in the freezing process).
Pour the whipped topping onto the lined baking dish.
Freeze for 1-2 hours.
Use a cookie cutter to cut out shapes. Store extra hearts (just leave them on the baking sheet) in the freezer for up to 2 weeks.