Preheat oven to 300 degrees F. Line a muffin tin with 6 foil baking cups (cakes will stick to paper liners). Lightly spray the liners with avocado oil spray.
Place the chocolate in a small bowl. Microwave in 30 second intervals, stirring after each microwave session, until the chocolate is completely melted. Set aside.
In a medium bowl, using an electric hand mixer set to the lowest speed, beat the cream cheese, vanilla and stevia until smooth. This should take no more than 30 seconds.
Add the melted chocolate and beat on low just until blended, scraping down the bowl with a rubber spatula as needed.
Add the egg and mix until just incorporated. Don't over mix.
Using a rubber spatula, give the batter one last mix to make sure everything is well incorporated.
Spoon the batter into the prepared muffin cups, smoothing out the tops. Bake until the centers of the cheesecakes are just a bit jiggly, about 15 minutes.
Place the muffin tin on a cooling rack and allow the cakes to cool completely, about 2 hours, before removing the liners and serving.
To ensure a smooth texture, all ingredients must be at room temperature, which is always the case when making cheesecakes. One option is to remove the cream cheese and egg from the fridge two hours before you plan to start mixing the ingredients. Alternatively, you can microwave the cream cheese for 30 seconds, and submerge the egg in warm water while you prep the ingredients.