Preheat your oven to 325 degrees. Also put a pot or kettle of water on to boil.
Combine milk, protein, extract, cocoa powder, sweetener and vanilla in a blender until thoroughly combined (about 15-20 seconds). Add eggs and blend again.
Place four ramekins (the ones shown are 4 oz.) in a baking dish. Divide mixture evenly among four ramekins. Now place the baking dish onto the middle rack of your preheated oven.
Pour boiling water into baking dish until it reaches half-way up the sides of the ramekins. (I advise doing this after you’ve placed the baking dish on your oven rack so you don’t slosh hot water on yourself!)
Bake for about 20 minutes, but start checking on it after about 10 minutes. The top will form a brownie like crust very quickly. When they are done they should still be a little jiggly when you shake the ramekin but the inside should not be liquid. If you bake them beyond the point of being jiggly that isn’t really a big problem. The final texture is just more like fudge and less like a custard.