Preheat the oven to 350°F (175°C). Butter a 9-inch springform pan and set aside.
Make the crust: In a food processor, pulse the Oreo cookies and 1 tablespoon granulated sugar until fine crumbs form. Add the melted butter and pulse until evenly moistened. (Or crush cookies in a zip-top bag with a rolling pin and mix with sugar and butter.)
Press the crumb mixture evenly into the bottom of the prepared pan and bake until set, about 8 minutes. Cool on a rack while you prepare the filling.
Melt the chopped bittersweet chocolate in a heatproof bowl set over barely simmering water, stirring until smooth. Remove and let cool to room temperature.
Make the filling: Using an electric mixer on medium speed, beat 32 ounces cream cheese, 1 1/4 cups plus 2 tablespoons granulated sugar, and 1/4 cup cocoa powder until light and fluffy, about 3 minutes, scraping the bowl as needed.
Beat in the eggs one at a time, mixing well and scraping the bowl between additions. Add the cooled melted chocolate and mix until just combined, finishing with a rubber spatula to ensure even texture.
Pour the filling over the baked crust and smooth the top. Bake until the center barely wiggles and the top looks dry, about 1 hour.
Cool the cheesecake 5 minutes, run a thin knife around the edge to loosen, then refrigerate uncovered and chill overnight.
Make the cherry topping: Drain and reserve 1/4 cup of juice from the thawed cherries. In a medium saucepan, combine the cherries (with remaining juice), 1/4 cup granulated sugar, and a pinch of salt. Cook over medium heat until it comes to a boil, about 5–10 minutes.
Whisk the reserved cherry juice with the cornstarch until smooth and stir into the boiling cherry mixture. Cook, stirring constantly, until thickened, about 1 minute. Remove from heat and stir in the lemon juice. Cool to room temperature, then chill at least 1 hour.
Make the whipped cream topping: Beat 4 ounces cream cheese, 1/4 cup granulated sugar, and 3/4 teaspoon vanilla extract with the whisk attachment until smooth, about 3 minutes. Slowly add 1 cup heavy cream, then increase speed and whip to stiff peaks.
Assemble: Remove the springform ring and place the cheesecake on a serving platter. Pipe a border of the whipped cream around the top edge and spoon the chilled cherry topping into the center. Garnish with chocolate shavings if desired.