In a small bowl, sift the flour, baking powder, baking soda and salt and set aside.
In a large mixing bowl, use a hand mixer to cream the butter and sugars together until fluffy. Mix in the egg, egg yolk, and vanilla extract until combined. Using a wooden spoon, gently mix through the dry ingredients, then fold in the candy buttons and chocolate chips.
Cover the mixing bowl and refrigerate for an hour.
Preheat the oven to 180C/350F. Line two large cookie sheets with parchment paper and set aside.
Using a cookie scoop, scoop out 12-16 portions of cookie dough. Place them on the two cookie sheets, leaving 1-2 inches apart so the cookies can spread.
Bake the cookies for 10-12 minutes, or until the edges are just done. Remove the cookies from the oven and let them cool completely.
Notes
* If your gluten free flour does not contain xanthan gum, add 1/2 teaspoon to the dough. My preferred brands are Bob's Red Mill and Doves Farm.TO STORE: Cookies can be stored at room temperature in an airtight container for up to one week. If you'd like them to keep longer, store them in the refrigerator. TO FREEZE: Place leftovers in a ziplock bag and store them in the freezer for up to 6 months.