1-Preheat oven to 325°F (163°C). Grease and line the bottom of a 9-inch springform pan with parchment paper to ensure easy removal later.

2-For the Shortbread Crust: Whisk 1 1/4 cups all-purpose flour, 1/2 cup powdered sugar, and a pinch of kosher salt in a bowl. Add 1/2 cup cold unsalted butter, cubed, and work it into the dry ingredients by hand until crumbly. Mix in 2 tablespoons milk until the dough is moist but crumbly, then press it into the bottom of the prepared pan and bake for 18 to 20 minutes. Keep the oven at 325°F.

3-For the Sugar Cookie Dough: In the same mixing bowl, beat 6 tablespoons unsalted butter, room temperature, and 3/4 cup granulated sugar until smooth. Mix in 2 tablespoons milk and 1/2 teaspoon vanilla extract. Stir in 1 cup all-purpose flour and 1/2 teaspoon kosher salt, then add 3 tablespoons jimmies sprinkles. Mix until the dough comes together, pinch off bite-sized pieces, and roll into balls; set aside.

4-For the Cheesecake Filling: Place a roasting pan on the bottom rack of the oven and bring a separate pot of water to boil. Beat the 4 (8-ounce) blocks full-fat cream cheese, room temperature, with 1 cup granulated sugar and 2 tablespoons all-purpose flour on low speed until smooth. Scrape the bowl, then mix in 1 teaspoon vanilla extract, 1/4 teaspoon almond extract (optional), and 3/4 cup sour cream, room temperature, on low. Scrape again and add 4 large eggs, room temperature, one at a time, mixing on low. Fold the cookie dough balls gently into the batter by hand.

5-Butter the sides of the cheesecake pan, pour in the batter, and place the pan on the middle rack above the roasting pan with boiling water to create a water bath. Bake for 1 hour and 15 minutes until the edges are golden and the center slightly jiggles. Turn off the oven, crack the door open, and leave the cheesecake inside for 45 minutes.

6-Remove the cheesecake and cool at room temperature for 30 minutes, then refrigerate and chill overnight for the best texture.

7-For the Frosting: After chilling, beat 6 tablespoons unsalted butter, room temperature, until smooth. Add 1/3 cup sour cream, 1 1/2 cups powdered sugar, and 1 teaspoon vanilla extract until creamy. Spread the frosting over the cheesecake and decorate with sprinkles.