In a small saucepan or a microwave-safe bowl, combine the heavy cream and chocolate. Gently heat the mixture, stirring often, until the chocolate melts and everything is smooth and glossy. If you're using the microwave, heat it in 30-second bursts at 50% power, stirring each time until melted.
In a large mixing bowl (I love using my stand mixer with the paddle attachment for this), beat the cream cheese and sugar together on low speed until fully combined. Don’t forget to scrape down the bottom and sides of the bowl so everything mixes evenly—keep beating until smooth and creamy.
Crack in the eggs one at a time, beating after each addition. Scrape the bowl as needed to keep everything nice and smooth.
Now stir in the vanilla extract, followed by the cocoa powder.
Next up, pour in that delicious melted chocolate and cream mixture. Beat on low speed just until everything is combined. Scrape down the bowl again and give it one final mix until it’s perfectly smooth.
Time to fill those cupcake liners! Use a small cookie or ice cream scoop to evenly divide the batter among the 12 liners. Fill them all the way to the top and smooth the tops with a spatula.
Bake for 20–25 minutes, then take them out and let them cool at room temperature for about an hour. After that, pop them in the refrigator for 2 hours or until they’re nice and firm. Once chilled, remove the cheesecakes from the muffin tin!