Preheat oven to 350°F. Line a 12-cup muffin pan with cupcake liners or oil the inside of small jam jars.
Make the graham cracker crust:
Stir together graham cracker crumbs, sugar, and melted butter. Press about 2-2 1/2 tablespoons of the mixture into the bottom of each muffin liner and press to compact.
Beat room temperature cream cheese with a hand mixer until fluffy. Beat in room temperature sour cream. Beat in egg, sugar, and vanilla extract. (Room temperature ingredients are a must to avoid lumps!)
Evenly divide (about 2-2 1/2 tablespoons each) cheesecake among crusts. Bake for 18-20 minutes, until they just begin to brown. Cool completely and refrigerate for at least 3 hours or overnight.
Serve plain or topped with whipped cream and berries.