01 - Preheat oven to 325°F. Line a 12-cup muffin tin with paper liners.
02 - Mix graham cracker crumbs, sugar, and melted butter in a bowl until combined. Divide mixture evenly among liners and press firmly into bottoms.
03 - Bake crusts for 5 minutes, then remove from oven and let cool while preparing filling.
04 - Beat cream cheese in a large bowl until smooth. Add sugar and beat well. Add eggs one at a time, mixing thoroughly after each addition. Mix in vanilla and sour cream until fully combined.
05 - Spoon cheesecake filling over cooled crusts, filling each cup about 3/4 full. Bake for 18-20 minutes until centers are just set. Cool completely in pan, then refrigerate at least 2 hours.
06 - Melt butter in a skillet over medium heat. Add diced apples, brown sugar, granulated sugar, cinnamon, nutmeg, lemon juice, and salt. Cook stirring occasionally until apples are tender, about 4-6 minutes.
07 - Stir oats and flour into apple mixture. Cook additional 2-3 minutes until mixture is crumbly and golden. Remove from heat and let cool.
08 - Top each chilled mini cheesecake with a generous spoonful of apple crisp mixture. Serve chilled or at room temperature.