01 - Preheat oven to 325°F. Line a standard 12-cup muffin tin with paper liners and set aside.
02 - In a medium bowl, combine graham cracker crumbs, melted butter, and sugar. Stir until the mixture resembles wet sand and holds together when pressed.
03 - Divide the crumb mixture evenly among the 12 lined muffin cups. Press firmly into the bottom of each cup using the back of a spoon or a small measuring cup to create a compact, even crust layer.
04 - In a large bowl, beat softened cream cheese and granulated sugar together with an electric mixer on medium speed until completely smooth and creamy, about 2 minutes. Scrape down the sides of the bowl as needed.
05 - Add the egg and vanilla extract to the cream cheese mixture. Beat on low speed until just incorporated. Gently fold in the sour cream with a spatula until evenly combined. Avoid overmixing to prevent air bubbles.
06 - Spoon or pipe the cheesecake filling evenly over each prepared crust, filling each cup nearly to the top. Smooth the surface with a small spatula or the back of a spoon.
07 - Bake for 18 to 20 minutes, or until the edges are set and the centers still have a slight jiggle when gently shaken. Do not overbake.
08 - Remove from the oven and allow the cheesecakes to cool in the muffin tin at room temperature for 15 minutes.
09 - Transfer the mini cheesecakes to a wire rack and let them cool completely to room temperature.
10 - Refrigerate the cheesecakes for at least 1 hour to allow them to set fully. Once chilled, add your choice of toppings and serve.