Place 16 ounces cream cheese in the bowl of a stand mixer (or large bowl if using an electric hand mixer). Place 1/2 cup sour cream and 2 large eggs on the counter. Let everything sit at room temperature until the cream cheese is softened. Meanwhile, make the crust.
Make the Crust:
Arrange a rack in the middle of the oven and heat the oven to 350ºF. Line the bottom and two opposite sides of a 9×9-inch baking pan with a sheet of parchment paper long enough to hang over the sides by 1 inch to form a sling.
Melt 5 tablespoons unsalted butter in the microwave or on the stovetop. Place 20 Oreo cookies and 1/2 teaspoon kosher salt in the bowl of a food processor fitted with the blade attachment. Pulse until finely ground, about 30 (1-second) pulses. Add the butter and pulse until the mixture resembles wet sand, about 15 (1-second) pulses.
Transfer the mixture to the baking pan. Press it evenly into the bottom with the bottom of a flat measuring cup.
Bake until the crust is just set and fragrant, about 10 minutes. Place on a wire rack and keep the oven at 350ºF.
Make the Filling:
Add 3/4 cup granulated sugar to the bowl of cream cheese. Beat with the paddle attachment on medium speed until smooth, about 1 minute. Stop and scrape down the sides of the bowl with a flexible spatula.
Add the sour cream, 3/4 cup smooth peanut butter, 1/4 cup chocolate-hazelnut spread, 1 teaspoon vanilla extract, and 1/2 teaspoon kosher salt. Beat on medium speed until just combined, 30 seconds to 1 minute. Scrape down the sides of the bowl again.
Beat in the eggs one at a time, beating after each addition until combined and the mixture is smooth. Pour into the crust and spread into an even layer.
Bake until the filling is just set but has a slight jiggle in the center still, 20 to 25 minutes. Place the pan on a wire rack and let cool completely, about 1 hour. Refrigerate for at least 4 hours or up to overnight.
Make the Ganache:
Place 8 ounces semisweet chocolate chips in a medium heatproof bowl. Heat 1 cup heavy cream in a small saucepan over medium-high heat until simmering. Pour over the chocolate chips and let sit for 2 minutes. Whisk until smooth and glossy.
Pour over the cheesecake in an even layer. Let sit at room temperature until the chocolate begins to firm up, about 15 minutes. Sprinkle with 1 teaspoon flaky sea salt. Refrigerate until set, at least 1 hour or up to overnight.
Grasping the excess parchment, lift the slab out of the baking dish and place on a cutting board. Cut into 16 pieces, dipping the knife in hot water and wiping it dry between each cut for the cleanest-looking pieces.