Preheat oven to 350F. Press cookie dough evenly into the bottom of a 9-inch springform pan, building it about 1/2 inch up the sides. Bake until just set and lightly golden at the edges, 12-14 minutes. The center should still look slightly underdone. Cool completely on a wire rack, about 30 minutes. Reduce oven to 325F.

Beat cream cheese and sugar on medium speed until completely smooth and fluffy, scraping down the bowl twice, about 3 minutes. Add sour cream and vanilla; beat until combined. Add eggs one at a time, beating just until incorporated after each. Do not overmix.

Pour batter over cooled crust. Bake at 325F until the edges are set but the center still jiggles slightly, 35-40 minutes. Turn off the oven, crack the door open with a wooden spoon, and let cool inside for 1 hour. This prevents cracking. Refrigerate at least 4 hours or overnight until completely cold and firm.

Melt 3/4 cup chocolate chips with 1/2 cup cream in a double boiler or microwave in 30-second bursts, stirring until smooth. Cool to room temperature, about 15 minutes. Meanwhile, whip remaining 1 cup cream with powdered sugar to medium peaks.

Fold one-third of the whipped cream into the cooled chocolate to lighten it, then fold in the remaining cream gently until no streaks remain. Spread mousse evenly over the cold cheesecake. Sprinkle with remaining 1/4 cup chocolate chips. Refrigerate at least 2 hours to set the mousse.

Run a thin knife around the edge of the pan before releasing the springform. For clean slices, dip your knife in hot water and wipe dry between cuts. Serve chilled.