Prep: Make sure your cream cheese, eggs, and sour cream come to room temp before you begin. If they're not at room temp, the filling will not turn out properly. Line a standard size muffin tin (not a jumbo or mini one) with muffin papers. Preheat the oven to 350 degrees F. Make the Crust: Stir together the crust ingredients until well combined. Press 1.5 TBSP of the crust mixture into each muffin paper. Bake the crusts for 5 minutes. Set aside while you make the filling. Leave the oven preheated to 350 degrees F.
Make the Cheesecake Filling: In a large mixing bowl, beat the softened cream cheese until smooth. Add sugar, and mix until just creamed together with the cream cheese, about 30 seconds. Don't over mix your batter. Add cocoa and mix until just combined. Add the eggs and vanilla and mix until just combined. Add the sour cream and mix until just combined. You will have a smooth batter that's not super thick and not super runny. If it has a few small lumps, that's fine. If it looks curdled, your ingredients were too cold.
Bake: Spoon 2 TBSP of the cheesecake batter into each of the pre-baked crusts. Bake the cheesecakes for 20-21 minutes. The centers will have a tiny wobble to them when you move the pan, and a toothpick inserted into the center will come out just about clean - it may have a tiny bit of thick batter on it. Set the pans aside to cool, and after they're cool enough to touch, use a spoon or butter knife to lift each cheesecake out of the pan. Let cool completely. (See make ahead tip below).
Make the Marshmallow Meringue: Ideally, you would make this on a day that's not super humid, but work with what ya got!Fill a small/medium pot with about two inches of water. Grab a heat safe bowl and place it over the water to make sure it sits high enough that it won't touch the water. Remove the bowl, and bring the water to a simmer over low heat. Place the egg whites, sugar, and cream of tartar in the bowl and place it over the simmering water. Whisk this mixture constantly while it cooks over the low simmering water - do this for 4 minutes. Set a timer. It will go from thick, to thinner + frothy. To test that it's done, carefully dip your finger into the mixture and rub it between your fingers - if it's smooth, and you can't feel any grainy-ness from the sugar, it's ready!Once that's done, remove the bowl from the heat, add the vanilla, and immediately begin mixing with an electric mixer (make sure the beaters are clean and dry!) on high speed for about 5 minutes. It's done when you can turn off the mixer, lift it straight up, and stiff peaks form and hold.
Serve + Store: Pipe or spoon the meringue onto the cheesecakes, and toast with a kitchen torch. Store leftovers in an airtight container in the fridge for 3-4 days. The meringue will begin getting soft as the days go by, but it'll still taste fine.
Make Ahead Tips: The cheesecakes can be made, cooled, and stored in the fridge 1 day before serving. Don't make the marshmallow meringue ahead. Make it just before you want to serve the cheesecakes.