Preheat your oven to 350 degrees F. Make sure it’s fully heated before you bake. Line a large baking sheet with parchment paper or a silicone mat to prevent sticking.
In a large mixing bowl, whisk together the all-purpose flour, baking soda, cream of tartar, and kosher salt. This ensures that the leavening agents are evenly distributed.
In another bowl, use an electric mixer to combine the unsalted butter, vegetable oil, 1/2 cup of the granulated white sugar, and powdered sugar. Beat until smooth and creamy. The mixture should be light in color and fluffy.
Add in the large egg, vanilla extract, and almond extract to the butter mixture. Mix until everything is combined thoroughly.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed just until combined. Avoid over-mixing to keep the cookies tender and soft.
Using your hands or a small scoop, roll the dough into approximately 24 balls, each about 2 tablespoons. Make sure they’re uniform in size for even baking.
Place the dough balls on the prepared baking sheet, spaced about 2 inches apart. This allows room for spreading during baking.
Pour the remaining 1/4 cup of granulated white sugar onto a small plate. Spray the bottom of a drinking glass with nonstick cooking spray, then press it into the sugar to coat.
Press the sugared glass gently onto each cookie dough ball to flatten slightly, re-coating the glass in sugar as needed to prevent sticking.
Bake the cookies for 8 minutes. They should be light in color and soft in the center; that’s perfectly fine! The cookies will firm up as they cool.
Once baked, let the cookies cool on the baking sheet for 5 minutes. After that, transfer them to a wire cooling rack to cool completely.
In a separate bowl, beat the remaining unsalted butter until smooth. Gradually mix in the powdered sugar until well combined.
Slowly stream in the heavy cream, vanilla extract, and almond extract. Beat until the frosting is smooth and spreadable. If it's too thick, add more cream. If too thin, incorporate a little more sugar.
Once the cookies are completely cooled, use a butter knife to spread the frosting over the tops generously. Add sprinkles on top for that extra pop of color!
Store your cookies in an airtight container at room temperature for up to 3 days. Enjoy!