Preheat the oven to 350°F. Line 5 muffin cups with foil liners and brush the liners with melted butter.
In a large bowl, use a hand whisk to mix the cream cheese, sweetener, and vanilla.
Add the egg and whisk just until incorporated. Don't overmix.
Transfer the batter to the prepared muffin cups, filling them almost full. Bake until set but not browned (the center should be almost firm), for 15-20 minutes.
Cool the cakes in the pan on a cooling rack for 15 minutes, then remove them from the pan and cool them directly on the rack for 30 more minutes. Don’t remove the liners yet. As the cakes cool, their center will slightly sink. Perfect for toppings!
Once the cakes reach room temperature, place them in a sealed container and refrigerate them for one hour, then remove the liners.
Make the Topping:
Place the heavy whipping cream, vanilla, sweetener, and cocoa powder in a mini food processor bowl (the volume of ingredients is too low for a standard-size food processor).
Process until the ingredients turn into thick whipped cream, about 1 minute. If you have a "grind" and a "chop" setting, use the "chop" setting. If needed, stop once to scrape the sides and bottom.
Top the cakes with the whipped topping and serve.
Video
Notes
The cheesecakes stick to standard paper liners (even well-greased) but not to greased foil liners.
To ensure a smooth texture, all the ingredients should be at room temperature. So try to remember to take everything out of the fridge at least an hour before you start mixing the ingredients. If you forget, you can soften the cream cheese in the microwave in 10-second sessions and dip the egg in a bowl of warm (not hot) water for a few minutes.
You can use a granulated sweetener in the cakes and a powdered one in the topping instead of stevia.
You can store these cakes in the fridge, in an airtight container, for up to five days. Remember to remove them from the fridge an hour before serving them. Cheesecake, like chocolate, is best at room temperature. You can also freeze these cakes in an airtight freezer-safe container for up to three months. Thaw them overnight in the fridge.
Nutrition info for one mini cake without the topping: Calories 172, Total Fat 17 g, Saturated Fat 9 g, Sodium 148 mg, Total Carbohydrate 2 g, Dietary Fiber 0 g, Sugars 2 g, Protein 4 g.