In a bowl, whisk together flour, baking soda, cream of tartar, and a pinch of salt. Set aside.

In a mixing bowl, beat butter on high speed until light and fluffy. Add oil and both sugars and beat to mix well. Scrape sides of the bowl, then add eggs, vanilla extract and butter extract. Beat again until well combined.

Add half of the flour mixture to the mixing bowl, then mix on low speed just until combined.  Add the other half of the flour mixture plus the colored sprinkles, and on low speed, mix again just until combined. Avoid overmixing.

Cover and chill the cookie dough for at least an hour, or overnight.

When ready to bake, preheat oven to 375 degrees F.  Position the baking rack in the upper third of the oven.

Place one baking sheet on top of another, then line the top pan with a sheet of parchment paper. Use a cookie scoop (this one is approximately 1.5 tablespoons) and place six scoops of cookie dough on the baking sheet.

Bake for 10 to 12 minutes – turning halfway through the baking time – until the edges of the cookies are very lightly golden brown. Remove from the oven and cool on the baking sheet for 2 to 3 minutes, then remove the cookies to a wire rack to finish cooling completely.

Repeat this process until you have baked all 30 cookies (five trays).