Preheat oven to 375°F (190°C). Line baking sheets with parchment paper.
In a medium bowl, whisk together flour, cocoa powder, baking soda, and salt.
1 1/2 cups all-purpose flour, 1/4 cup unsweetened cocoa powder, 1 teaspoon baking soda, 1/4 teaspoon salt
In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
1/2 cup unsalted butter, softened, 3/4 cup granulated sugar, 1/4 cup packed light brown sugar
Beat in the egg and vanilla extract until well combined.
1 large egg, 1 teaspoon vanilla extract
In a small bowl, combine vinegar, red food coloring, and buttermilk.
1 teaspoon white vinegar, 1 tablespoon red food coloring, 1/2 cup buttermilk
Gradually add the wet ingredients to the dry ingredients, mixing until just combined. Do not overmix.
Cover the dough and chill for at least 30 minutes. (This helps prevent spreading!)
Roll the dough into 1-inch balls. Roll each ball in granulated sugar.
Granulated sugar, for rolling
Place the sugared dough balls onto the prepared baking sheets, about 2 inches apart. Bake for 8-10 minutes, or until the edges are set.
Immediately after removing from the oven, gently press a Hershey's Kiss into the center of each cookie.
36 Hershey's Kisses, unwrapped
Let the cookies cool completely on the baking sheets before transferring them to a wire rack. Serve and enjoy your delicious Red Velvet Peanut Butter Blossoms!
