Add both types of sugar and room temperature butter into a mixing bowl. Beat for about 1-2 minutes until well-combined. You can use a hand mixer or a stand mixer fitted with a paddle-shaped attachment.
Add the egg and vanilla extract. Beat for 1-2 minutes or until well-combined.
Stir flour with baking soda, baking powder, and salt in a small bowl. Add the flour mixture to the mixing bowl. Mix over low speed until half-combined (the flour shouldn't be fully incorporated at this point).
Roughly chop the candies and chocolate eggs (I cut small eggs only in half). You should have about 2 cups of chopped sweets.
Add the candies to the cookie batter. Mix over low speed until evenly distributed. Don't mix the cookie dough for too long.
Chill the dough for 30 minutes (or longer) in the fridge. This step is optional but recommended. You can bake the cookies right away but they will be quite flat. If you want thicker cookies, chill the dough for a minimum of 4 hours or overnight. The cookies on the photos were chilled only for about 20 minutes because I haven't had much time that day (they were still super delicious!). I baked the remaining cookies the next day, and there were absolutely perfect - a little bit crunchy at the edges, super soft and thick in the middle.
Scoop the dough with a 2-tablespoon scoop (each cookie dough ball should weigh 40g). Roll each piece of dough into a ball.
Place the cookies about 2-inches (5 cm) apart on a baking sheet lined with parchment paper. Bake the cookies in batches in an oven preheated to 350°F/180°C for about 11 minutes or until the edges of the cookies are golden but the tops pale and soft (they will finish baking on the baking sheet). Leave the cookies for about 5 minutes on the baking sheet then transfer using a spatula to a cooling rack.