Preheat the oven to 350 degrees.
In a medium bowl, whisk the flour, baking powder, baking soda and salt together. Then set aside the flour mixture.
2 cups (250 g) all-purpose flour, spooned and leveled, ½ teaspoon baking soda, ½ teaspoon baking powder, ½ teaspoon salt
In a large bowl, cream the butter, brown sugar and granulated white sugar together with an electric mixer on high speed until light and fluffy, 2-3 minutes. (You can use a stand mixer fit with a paddle attachment.)
¾ cup (168 g) unsalted butter, softened, ¾ cup (165 g) light brown sugar, packed, ¼ cup (50 g) granulated white sugar
Add in the egg yolks, vanilla extract, butter extract and melted butterscotch chips and mix on medium speed until pale in color and fluffy, 1-2 minutes. Scrape the sides of the bowl as necessary.
2 egg yolks, at room temperature, 1 tablespoon vanilla bean paste or extract, 1 ½ teaspoon butter extract, ¼ cup (50 g) butterscotch chips, melted and slightly cooled
Add the dry ingredients to the wet ingredients and mix on low speed just until combined.
Mix the butterscotch chips into the dough with a rubber spatula.
½ cup (100 g) butterscotch chips
Scoop the dough with a large cookie scoop into 2 tablespoon portions.
Arrange the cookie dough balls 6 at a time, 2 inches apart, on a parchment paper lined baking sheet. Bake the cookies for 10-11 minutes.Right after baking, scoot a large circular cookie cutter around the cookies to give them a perfect circular shape.
Let the cookies cool on the cookie sheet for five minutes then transfer them to a wire rack to completely cool.