• In a large bowl, use a hand mixer on medium speed to beat sugar, ½ cup butter, and shortening until well blended. Add egg and vanilla. Beat until the mixture is smooth.
• Mix in gluten-free flour, baking powder, and salt. The dough will be crumbly.
• Press the dough together to form a ball. Cut the dough in half. Wrap each half in plastic and refrigerate for 1 hour (up to 2 days).
• Preheat oven to 375℉. For easy cleanup, cover 2 baking sheets with parchment paper or silicone mats.
• Leave half the dough in the fridge. Roll out the other half of the dough to ¼-inch thick. To prevent sticking, roll the dough between two sheets of wax paper or use flour to lightly dust your work surface.
• Cut out cookie hearts with a 3-inch heart-shaped cookie cutter. Place hearts 1 inch apart on the prepared baking sheets.
• Bake cookies at 375℉ until the edges are golden, approximately 7-8 minutes. Allow cookies to cool on the baking sheet for two minutes. After two minutes, carefully transfer the cookies to a cooling rack until completely cool, approximately 12 minutes.
• Repeat steps 5-7 with the remaining refrigerated cookie dough.

Decorate

• While the cookies are cooling, place chocolate morsels and 1 tablespoon of butter in a microwave-safe mug or small bowl. The container should be wide enough to fit the heart-shaped cookies for dipping. Microwave for 30 seconds. Stir. Melt chocolate in additional 15-20 second increments, stirring each time.
• Pour Valentine sprinkles into a small condiment bowl.
• Dip each cookie into the melted chocolate, approximately 1 inch deep, and then immediately dip in the Valentine's sprinkles. Return to the cooling rack to dry, about 30 minutes. Optionally, mix and match, dipping some cookies in chocolate only and some in chocolate and sprinkles.