• Preheat your oven to 350°F.
• Lightly coat 1³⁄₄-inch muffin cups with cooking spray.
• In a large bowl, beat the softened butter with a mixer on medium speed for about 30 seconds.
• Add powdered sugar, baking powder, and salt.
• Beat until the mixture becomes creamy, scraping the bowl as needed.
• Beat in the egg and vanilla.
• Gradually beat in the flour.
• Divide the dough in half.
• Stir red sprinkles into one half of the dough and green sprinkles into the other half.
• If needed, cover and chill the dough for 30 to 60 minutes, or until it's easy to handle.
• Shape the dough into 1-inch balls and press these balls onto the bottoms and up the sides of the prepared muffin cups.
• Bake for 8 minutes or until the edges are lightly browned.
• Remove from the oven and press the centers with the rounded side of a measuring teaspoon.
• Cool the tassies in the muffin cups on wire racks for 5 minutes.
• Afterward, remove them from the muffin cups and continue to cool them on wire racks.
• Fill the cooled tassies with the Cream Filling and top with additional sprinkles.

Cream Filling:

• In a medium bowl, beat ¹⁄₄ cup softened butter with a mixer on medium speed for about 30 seconds.
• Add 1¹⁄₄ cups powdered sugar, 1 tablespoon half-and-half or milk, and ¹⁄₄ teaspoon vanilla.
• Beat until the mixture becomes fluffy.

To Store:

• Layer the cookies between sheets of waxed paper in an airtight container.
• Store in the refrigerator for up to 3 days or freeze them for up to 1 month.