Make the crust – Crush biscuits into fine crumbs. Mix with melted butter and sugar until it resembles wet sand. Press into springform pan; refrigerate.

Make the blackberry purée – Blend blackberries until smooth; strain through fine mesh to remove seeds. Measure 180g (3/4 cup).

Make the filling – Preheat oven to 325°F. Beat cream cheese and crème fraîche until smooth. Add sugar and beat well. Add eggs one at a time, beating briefly after each. Fold in blackberry purée until evenly colored.

Bake – Pour filling over crust. Bake at 325°F for 50-65 minutes until edges are set and center jiggles slightly. Turn off oven, crack door, cool inside for 15 minutes. Cool to room temperature, then refrigerate 4+ hours or overnight.

Make the compote – Cook blueberries and sugar over medium heat, stirring occasionally, until thickened and jammy. Cool completely.

Make the whipped topping – Beat cream cheese until smooth. Add heavy cream, powdered sugar, and lemon zest. Whip until light and holding medium peaks.

Assemble – Spoon cooled blueberry compote over chilled cheesecake. Add lemon whipped cream topping. Slice and serve.