Step 1: In a large bowl, cream together the softened butter and granulated sugar until light and fluffy, about 2-3 minutes.
Step 2: Beat in the egg and vanilla extract until well combined.
Step 3: In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined and a soft dough forms. Do not overmix.
Step 4: Divide the dough in half, flatten each half into a disc, wrap in plastic wrap, and chill in the refrigerator for at least 30 minutes (or up to 2 days).
Step 5: Preheat your oven to 375°F (190°C). Lightly grease a mini muffin pan or cookie shot mold.
Step 6: On a lightly floured surface, roll out one disc of chilled dough to about 1/4-inch thickness. Using a round cookie cutter slightly larger than your muffin pan cups (or according to your mold instructions), cut out circles.
Step 7: Gently press each dough circle into the prepared muffin pan cup, forming a cookie cup shape. Trim any excess dough from the tops.
Step 8: Bake for 10-12 minutes, or until the edges are lightly golden. The center may still look slightly soft but will firm up as it cools.
Step 9: Remove from the oven and, while still warm, use the back of a spoon or a small, rounded object to gently reshape the indentation if needed. Let cool in the pan for 5-10 minutes before carefully removing them to a wire rack to cool completely.
Step 10: Once the cookie cups are completely cool, melt the white chocolate chips or candy melts in a microwave-safe bowl in 30-second intervals, stirring until smooth. Alternatively, use a double boiler.
Step 11: Spoon about 1-2 teaspoons of melted chocolate into each cooled cookie cup. Using the back of the spoon, spread the chocolate to coat the inside walls and bottom of the cup, creating an even layer. Invert the cups briefly to remove any excess chocolate.
Step 12: Place the lined cookie cups on parchment paper and refrigerate for 10-15 minutes, or until the chocolate is fully set. Fill and serve immediately with your favorite festive beverages or desserts!