01 - Preheat oven to 320°F. Line base of 9-inch springform pan with parchment paper.
02 - Crush biscuits into fine crumbs. Mix with melted butter and sugar. Press firmly into pan base. Bake for 10 minutes, then cool.
03 - Beat cream cheese and sugar until smooth. Add eggs one at a time, mixing gently. Blend in vanilla, sour cream, and flour until just combined.
04 - Pour filling over cooled crust. Bake 45-50 minutes until edges are set but center is slightly wobbly. Turn off oven, crack door, and cool 1 hour. Refrigerate at least 2 hours.
05 - Combine blueberries, sugar, and lemon juice in saucepan. Cook over medium heat 5-7 minutes until berries burst. Purée and strain to remove seeds.
06 - Sprinkle gelatin over water, let bloom 5 minutes, then warm gently until dissolved. Stir into warm blueberry purée. Cool to room temperature.
07 - Whip heavy cream to stiff peaks. Gently fold in cooled blueberry mixture until smooth and airy.
08 - Spread mousse evenly over chilled cheesecake. Refrigerate at least 2 hours until set.
09 - Decorate with fresh blueberries and mint leaves before serving.