Preheat oven to 350°F. Grease the interior of two 8-ounce ramekins with cooking oil spray.
In a medium bowl, add eggs and heavy cream and whisk until mixed.
Add in melted butter and vanilla (if using). Whisk until evenly combined.
In a separate medium bowl, add cocoa powder and sugar. Whisk to evenly combine, making sure to break up any cocoa clumps.
Add dry ingredients into the wet ingredient bowl. Whisk until batter is smooth. Divide batter evenly between the two prepared ramekins.
Place ramekins onto a baking sheet. Place into the middle of the oven and bake for about 13-15 minutes or until the edges of the cake are set (the edges should start to slightly pull away from the ramekin) and the center is still jiggly. I recommend you start watching and checking on the cake after 12 minutes.
Use a thin spatula or knife to loosen the edges of the cake. You will want to remove the cake from the ramekin while it is still hot, otherwise, the cake will continue to cook. Place a plate on top of the ramekin. Press the plate to the ramekin and swiftly flip upside down, so that the plate is now at the bottom and the ramekin is upside down. Gently tap the ramekin to ensure cake has slid onto plate. Lift up ramekin. Make sure to do this all while using oven mitts as the ramekin should still be very hot. Serve immediately with your choice of toppings.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.