Preparing the Crust

1. Preheat your oven to 350°F. Line a muffin tin with 18 cupcake liners.
2. Using a food processor, pulse the Oreo cookies into fine crumbs. Add the melted butter and mix until the crumbs are evenly coated.
3. Divide the crumb mixture among the cupcake liners, pressing it down firmly to create a compact crust. Set aside while you prepare the filling.

Making the Cheesecake Filling

1. In a large mixing bowl, beat the softened cream cheese and granulated sugar until smooth and creamy.
2. Add the sour cream, vanilla extract, and flour, and continue beating until fully incorporated.
3. Slowly pour in the melted dark chocolate and mix until the batter is rich and chocolatey. Use a spatula to scrape down the sides of the bowl for an even mixture.
4. Add the eggs one at a time, beating on low speed just until combined. Avoid overmixing to prevent air bubbles in the batter.

Baking the Cheesecakes

1. Spoon the cheesecake filling evenly onto the prepared crusts, filling each liner almost to the top.
2. Place a large sheet pan filled halfway with water on the bottom rack of the oven to create a humid baking environment. This helps prevent cracks in the cheesecakes.
3. Bake the cheesecakes on the middle rack for 22-23 minutes, or until the edges are set and the centers have a slight jiggle.
4. Remove from the oven and let the cheesecakes cool in the pan for 15 minutes. Transfer them to a wire rack to cool completely, then refrigerate for at least 2 hours to set.

Preparing the Chocolate Mousse

1. Beat the softened cream cheese in a mixing bowl until smooth. Gradually add the melted dark chocolate and mix until well combined.
2. Gently fold in the thawed Cool Whip, creating a light and fluffy mousse.
3. Transfer the mousse to a piping bag fitted with a 1M star tip for a decorative finish.

Assembling and Decorating

1. Pipe the chocolate mousse onto the chilled cheesecakes in a beautiful swirl.
2. Drizzle hot fudge sauce over the mousse and sprinkle mini chocolate chips for added texture.
3. Finish each cheesecake with a mini Oreo cookie on top.