Pre-heat oven to 450 degrees F.
Bring dark chocolate and unsalted butter to a small/medium micrwavable bowl.
Microwave for 30 seconds at 50% power, remove from microwave, stir with a spoon, bring back to microwave. Repeat until all chocolate is melted. Note: do not short cut this step to void burning chocolate!
In another small/medium bowl, whisk together egg, egg yolk, flour, and sugar.
Add melted chocolate into egg mixture. Whisk to combine.
Generously grease two 6 oz ramekins using unsalted butter. Can grease with vegetable oil or canola oil as well.
Divide mixture equally into the two ramekins. Place ramekins on baking sheet.
Bake for 12-13 minutes. Remove ramekins promptly. Let it rest for 1 minute (don't let it sit for too long as it will continue to cook and it will not longer be gooey in the middle). Invert ramekins onto plates.
Top with vanilla ice cream. Serve and enjoy!