Heat oven to 350°F. Process gingersnaps, walnuts, and confectioners’ sugar in a food processor until finely ground. Add butter; pulse until evenly combined.
Transfer to a 9″ x 12″ rectangular baking dish, and press crumbs into the bottom and halfway up the sides of the pan; set aside.
Clean food processor, and then combine quark, cane sugar, pumpkin puree, pumpkin spice, vanilla, salt, and eggs; puree, stopping to scrape down the bowl with a rubber spatula at least once, until smooth.
Pour into crust; bake until browned on top and the middle jiggles slightly when the pan is tapped, about 1 1⁄2 hours.
Let cool to room temperature; chill until set, at least 4 hours or overnight.