Prep the pan: Line a 12-cup muffin tin with paper liners. Heat oven to 325°F (165°C).
Make the crust: Stir graham crumbs, brown sugar, salt, and melted butter until the mixture looks like damp sand.
Portion and press: Divide crust among liners (about 1 heaping tablespoon each).
Press firmly with the bottom of a small glass or spoon.
Par-bake: Bake crusts for 6–7 minutes. Cool while you mix the filling.
Beat the cream cheese: In a bowl, beat softened cream cheese on medium until smooth and fluffy, about 1–2 minutes. Scrape the bowl.
Add sugar: Beat in granulated sugar until silky, 1 minute more.
Mix in the rest: Add sour cream, vanilla, lemon zest, and lemon juice.
Blend on low until combined.
Add eggs: Beat in eggs one at a time on low speed just until incorporated. Do not overmix.
Fill cups: Spoon batter evenly over crusts, almost to the top.
Bake: Bake 15–18 minutes, until edges are set and centers still jiggle slightly. They’ll finish setting as they cool.
Cool and chill: Cool in the pan 20 minutes, then transfer to a rack. Chill at least 2 hours, preferably overnight.
Top and serve: Gently pat mandarin segments dry, then arrange on each cheesecake.
Add a small dollop of whipped cream if you like.