Preheat your oven to 350°F (180°C). Line a baking sheet with parchment paper or a silicone baking mat and set aside.
In a large mixing bowl, cream together the salted butter, granulated sugar, and brown sugar for 2 minutes or until light and fluffy.
Add the egg and vanilla extract to the butter and sugar mixture. Beat until well combined.
Add the dry ingredients (flour and baking powder) to the wet ingredients, mixing until a soft cookie dough forms.
Fold in the crushed cadbury eggs until evenly distributed throughout the cookie dough.
Using a rolling pin, roll the dough out until about 1/2 inch thick.
Use desired cookie cutters to cut out the cookies. Transfer to the prepared baking sheet.
Bake in the preheated oven for 7-9 minutes or until the edges are lightly golden. Be cautious not to overbake to maintain a soft and chewy texture.
Remove the cookies from the oven and allow them to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
Top with frosting, if desired. Enjoy!