Heat oven to 325 F. Line the bottom of a 9-inch springform with parchment and lock the ring. Wrap the outside with two layers of heavy foil to prevent leaks.

Cream butter and sugar until fluffy, beat in egg and vanilla, then mix in dry ingredients just to combine for the crust. Press dough evenly into the bottom of the pan, going up the sides about 1 inch. If using store-bought dough, press it right in. Dock with a fork. Par-bake for 10 minutes, then cool for 5 minutes.

Beat cream cheese on low to medium-low until smooth. Add sugar, cornstarch, and salt, mixing on low until combined. Blend in sour cream and vanilla. Beat in the eggs one at a time on low, just until blended. Do not overmix.

Pour filling over the crust. Set the pan inside a larger roasting pan. Pour hot water into the outer pan to reach halfway up the springform. Bake for 55 to 70 minutes. The edges should look set and the center should have a gentle wobble about 2 inches wide.

Turn off the oven, crack the door, and let the cheesecake rest inside for 45 to 60 minutes. Move to a rack and cool for 1 more hour. Chill uncovered until cold, then cover and chill for at least 6 hours or overnight.

Run a thin knife around the edges, unlock the ring, and slice with a hot, dry knife for clean cuts. Add whipped cream and sprinkles if you like.