Preheat the oven to 350°F. Line baking sheets with parchment paper.
In a medium bowl, whisk together the flour, baking powder, and salt to combine.
Using mixer, on medium speed beat the butter and sugar until light and fluffy, 2 to 3 minutes. Add the egg, egg yolk, and vanilla, and beat until combined.
Slowly beat in the flour mixture with some yellow and green food coloring and mix dough on low speed until cookie dough and color is dispersed throughout the cookie dough evenly. Add more yellow or green food coloring as needed without overmixing cookie dough too much.
Place the remaining 1/4 cup sugar in a shallow dish. Using a small, medium or large spring-loaded scoop, divide the dough into balls, then roll in sugar to coat evenly. Place the dough balls on the prepared baking sheets, spacing 2 inches apart and very slightly flatten cookies. Cookies will spread out.
Add a jumbo heart sprinkle on top of each of your cookies. If you want larger hearts, after the cookies have baked and cooled, melt some red colored chocolate melts and pipe one on top of cookies or use red frosting and pipe heart on top of cookies and sprinkle with red sugar. Bake for 8-10 minutes for small, 10-12 for medium and 12-14 for large cookies or until the cookies set and begin to brown.
Cool cookies for 5 minutes before removing to a wire rack to cool completely.
See step 5 for how to make larger hearts in middle, if desired after the cookies have cooled completely before adding piping designs on top.