Measure the flour, baking powder, and salt into a medium sized bowl and set aside for later.
Combine the two sugars and butter in the bowl of a stand mixer that is fitted with the paddle attachment, or a mixing bowl with a hand mixer. Mix on low speed until fully incorporated and fluffy, about 1 to 2 minutes.
Scrape the sides of the bowl and add the eggs and vanilla. Stir 30 seconds more, or until the eggs have combined into the dough.
Pour the dry ingredients to the mixing bowl with the butter. Stir on low speed for about 1 minute longer, or until the dough starts to form. Fold in 3/4 cups of candies.
Chill dough for 30 minutes or up to three days.
Preheat the oven to 350 degrees and line cookie sheets with parchment paper or a silicone baking mat. Roll the dough into 1″ rounds and place 2 inches apart on the prepared baking trays.
Press additional candies onto the tops of each cookie (you can also stir these in to save a step if desired). Bake 8-10 minutes or just until the edges start to lightly brown.
Remove the cookies from the baking tray and onto a cooling rack. Enjoy warm or after they have cooled.
Notes
Slow down. You want to keep your mixer on low speed. I know it can be tempting to speed things up but you do not want to heat the butter too much.
Try to use room temperature ingredients. For this recipe, specifically, you need to make sure that the butter and eggs are left out of the refrigerator for at least 20 minutes.
Chill your dough. All of that mixing can cause the butter to spread. Giving the dough a little time to relax and firm up helps hold things together.