Microwave the chocolate alone on 50% for 2 minutes. Stir and add in the butter. Microwave an additional 1 minute on 50%.
Make the batter
Beat the eggs, vanilla, sat, and stevia in a stand mixer, about 5 minutes. Combine the chocolate and butter mixture with the egg mixture. Stir to combine. Sprinkle the flour over the combined mixture. Fold to combine completely.
Pour the batter into 8 prepared ramekins and bake for about 12 to 13 minutes, until the cakes have puffed about an inch above the ramekins.