In the bowl of a stand mixer, cream the butter and sugar until light and fluffy. Beat in the egg and vanilla until fully incorporated.
3/4 cup butter, 1 cup granulated sugar, 1 large egg, 1 tsp. vanilla extract
Add the flour, baking powder, and salt to the bowl. Beat on low speed at first, then increase as needed, until the dough is well combined. The dough will be soft and sticky.
3 cups all-purpose flour, 1 tsp. baking powder, 1/2 tsp. table salt
Chill the dough in the fridge for at least one hour. Longer is fine.
Preheat the oven to 350℉ and line a cookie sheet with parchment paper or a silicone mat.
Flour the surface where you'll be rolling out the dough. Using a rolling pin, roll the dough to about ¼ inch thick, then cut out hearts with a heart-shaped cookie cutter. Place them on the prepared cookie sheets 1 to 2 inches apart; they won’t spread much. I used a 3.15-inch heart-shaped cookie cutter, which is linked above in the recipe card.
Bake for 10 to 12 minutes, until the bottoms are just starting to turn lightly golden but the cookies remain mostly white. Immediately transfer them from the hot cookie sheet to a cooling rack.
Once the cookies have cooled, divide the frosting into three bowls. Add pink food coloring to one, red to another, and leave the last one white. Stir the colored frostings until evenly mixed.
1 can vanilla frosting, red and pink food coloring
Frost the cookies with a knife, then use a piping bag to write cute sayings on them if desired.