Beat the cream cheese and sugar in a stand mixer with a paddle attachment on medium speed until very smooth, about 1 minute, scraping the sides of the bowl as necessary. Turn the mixer to low, add the sour cream and cocoa powder and mix until combined, scraping the sides of the bowl as necessary. Add the melted chocolate and then the eggs one at a time, mixing on low speed after each egg just until mixed; do not overmix. Pour the filling over the crust and spread into an even layer.
4 8 oz. of room temperature cream cheese, 1 1/2 cups granulated sugar, 1/2 cup sour cream, 1/4 cup unsweetened cocoa powder, 4 large eggs