Get Ready: Preheat your oven to a cozy 350°F (175°C). Line a large baking sheet with parchment paper to prevent sticking, and set it aside.
Cream It Up: In a stand mixer or a large bowl with a hand mixer, beat the softened butter with the brown sugar and granulated sugar until the mixture is wonderfully smooth and light.
Add Wet Goodies: Mix in the egg yolk, vanilla extract, and that vibrant red food coloring. Continue to mix until everything is beautifully combined and boasts a uniform, bright red hue.
Combine Dry: Gently add the all-purpose flour, cocoa powder, baking powder, and salt to the wet mixture. Mix on low speed just until the dry ingredients are fully incorporated and the flour streaks disappear. Be careful not to overmix!
Roll into Sparkle: Using a tablespoon, scoop out about 18 equally sized portions of cookie dough. Roll each portion between your palms to form a smooth ball. Next, roll each cookie dough ball generously in the red sanding sugar until it's completely coated.
Bake to Perfection: Place the glistening cookie balls onto your prepared baking sheet, leaving a little space between each for even baking. Bake for 10 minutes, or until the edges are just set and the centers look slightly soft.
Add the Kiss: As soon as you pull the hot cookies out of the oven, immediately place one Hershey's Kiss into the center of each warm cookie. Press down gently so it settles nicely.
Cool Down: Let your beautiful blossom cookies cool on the baking sheet for about 10 minutes to firm up. Then, carefully transfer them to a wire rack to cool completely. Enjoy your homemade, heartfelt treats!