Whisk together all-purpose flour, cornstarch, baking powder, salt, and baking soda in a medium mixing bowl. Set aside.
2 ⅔ cups all-purpose flour, 1 tablespoon cornstarch, 1 ½ teaspoons baking powder, 1 teaspoon fine sea salt, ½ teaspoon baking soda
In a large mixing bowl using a hand mixer or in the bowl of a stand mixer, beat the butter, granulated sugar and light brown sugar together on medium speed for 3 to 4 minutes, scraping down the sides and bottom of the bowl as needed. The mixture should be light and fluffy.
1 cup unsalted butter, 1 ¼ cups granulated sugar, ¼ cup light brown sugar
Reduce speed to low and add in the egg followed by the egg yolk, mixing until fully combined. Next, add in the vanilla extract and almond extract. Continue mixing until everything is incorporated, scraping down the sides and bottom of the bowl as needed.
1 large egg, 1 large egg yolk, 1 ½ teaspoons vanilla extract, ½ teaspoon almond extract
With the mixer still on low speed, add in the dry ingredients a half cup at a time, scraping down the sides and bottom of the bowl as needed. Continue mixing until you no longer see any white streaks from the flour. Lastly, add in the jimmies sprinkles and mix until fully combined. ½ cup jimmies sprinkles
Line a baking sheet or lidded container with parchment paper or silicone baking mat.
Scoop cookie dough with #40 scoop (two tablespoons). I like to scoop “heaping” scoops with the #40 scoop. My preference is for larger sugar cookies, but if you would prefer smaller cookies, you can adjust the size of your scoop. Place each cookie dough ball on the prepared baking sheet. When you have finished scooping all the cookie dough, place the cookie sheet in the refrigerator to chill for 2 hours or overnight.