In a medium bowl, whisk together 3 cups flour, 1 teaspoon baking powder, and 1 teaspoon salt. Set aside.
In a large bowl, beat 1 cup butter and 4 oz cream cheese until smooth and creamy.
Add 1 cup sugar and mix until light and fluffy.
Beat in 1 large egg and 1 teaspoon vanilla extract, scraping down the sides as needed.
Gradually add the dry ingredients and mix just until combined. The dough will be thick.
Cover and chill the dough for 1 hour (or up to 3 days). If chilled longer, let sit at room temperature for 15–30 minutes before baking.
Preheat oven to 350°F. Line baking sheets with parchment paper.
Scoop about 1 tablespoon dough and roll into balls.
Roll each ball in ½ cup sanding sugar (pink/red mix) to coat.
Place cookies 2 inches apart on the baking sheet. Gently flatten.
Bake for 12 minutes, or until edges are lightly golden.
Cool for 3–4 minutes, then press 1 chocolate heart into the center of each cookie.
Chill cookies for 10–15 minutes until chocolate is set.