Cream the Butter and Sugar: In a large mixing bowl, combine the softened butter and granulated sugar. Beat using an electric mixer on medium speed until it’s light and fluffy, usually about 3-4 minutes., Add the Egg and Vanilla: Mix in the egg and vanilla extract until fully incorporated., Combine Dry Ingredients: In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add this mixture to the wet ingredients, blending until just combined. Do not overmix., Chill the Dough: Cover the dough with plastic wrap and chill it in the refrigerator for about 30 minutes; this will help the cookies maintain their shape while baking., Form the Cookie Cups: Once chilled, scoop about 1 tablespoon of dough and roll it into a ball. Place each ball into the prepared muffin pan and press down slightly to form a cup shape., Bake the Cookie Cups: Bake in the preheated oven for 10-12 minutes or until the edges begin to turn golden brown. Make sure they don’t overbake, as you want the centers to remain soft., Create the Center Indentations: As soon as they come out of the oven, use the back of a tablespoon or a small measuring cup to press gently in the center of each cookie while they are still warm. This will create the space for the frosting and candy., Cool Completely: Let the cookie cups cool in the pan for about 5 minutes before transferring them to a wire rack to cool completely., Prepare the Frosting: In a mixing bowl, beat the softened butter on medium speed until smooth and creamy. Gradually add the powdered sugar, one cup at a time. Mix until well combined. Add the milk and vanilla extract to the mixture. Beat on high speed for about 3 minutes, until light and fluffy. Add more milk if necessary to reach your desired piping consistency., Frost the Cookie Cups: Using a piping bag fitted with a star tip, pipe the frosting into each cookie cup. You can swirl it on top for a cute basket look or simply fill the center., Add Your Candies: Once frosted, fill the center of each cookie cup with colorful candies, chocolate eggs, or jellybeans. Feel free to get creative with the toppings., Decorate as Desired: You can sprinkle edible glitter or shredded coconut on top to mimic grass. Alternatively, use chocolate curls or sprinkles for added texture.