Preheat oven to 350°F, and grease the bottom of a 9-inch springform pan. Line pan with greased waxed paper or parchment paper.
Combine butter, sugar, and cocoa powder. Stir in wafer crumbs. Press evenly over bottom of the springform pan and bake for 10 minutes. Cool pan and grease sides, if desired.
4 tablespoons unsalted butter, ¼ cup sugar, ¼ cup cocoa, 1 package vanilla wafers
Make the filling:
Set oven to 325°F.
In the bowl of a stand mixer, beat cream cheese and sugar until light and fluffy. Add eggs one at a time while beating. Stir in sour cream, Bailey's, and vanilla. Pour ⅔ of the cheesecake mixture over the crust.
To the remaining mixture, stir the melted chocolate. Spoon the chocolate mixture by large spoonfuls over the plain cheesecake mixture.
6 ounces semi-sweet chocolate
Bake for about 1 ½ hours, until the center is raised and set. Let cool to room temperature. Remove springform pan sides before topping if you prefer the look of ganache drips on the sides of the cheesecake.
Make the topping:
Mix chopped chocolate with whipping cream and butter and melt in a saucepan on the stove or in a bowl in the microwave on 50% power in 30-second intervals. Stir in vanilla. Use a wire whisk to get the ganache nice and smooth, then let it cool a bit. Spread over top of the cheesecake.
5 ounces semi-sweet chocolate, ½ cup heavy whipping cream, 2 tablespoons butter, ½ teaspoon vanilla extract
Refrigerate at least 6 hours, or overnight.
Notes
Source: Adapted from a recipe by Kerry M.You're Gonna Bake It After Allbakeitafterall.com