Heat the oven to 375F.
Butter 8 small ramekins and coat each ramekin with butter.
Melt the 2 T of butter in a medium saucepan.
Add the flour and whisk together to make a roux, about a minute.
Slowly add the milk whisking constantly, until all the milk has been incorporated and the mixture is smooth.
Bring to a boil and reduce to a simmer and cook until the mixture is thick and smooth, about 3-5 minutes.
Remove from the heat and add the chocolate. Stir to melt and combine the chocolate with the sauce base.
Once all the chocolate has melted and the mixture is well mixed whisk in the egg yolks and salt. At this point you can set it aside for several hours at room temperature. If the mixture becomes too thick, loosen with water before folding into the egg whites.
In a large bowl beat the egg whites until frothy, add the cream of tartar and beat until they form soft peaks. Add the sugar and beat until smooth, but not stiff.
Fold about 1/3 of the chocolate mixture into the whites, to break up the whites a bit. Add the remaining chocolate mixture and fold until blended.
Spoon the mixture into the ramekins, filling them quite full. Place the ramekins in a pan with edges and add enough hot water to come about 1/3 of the way up the sides of the ramekins.
Place in the oven and bake until raised and puffy. They will still be soft and pudding-like in the center, about 15 minutes.
Use tongs to remove the ramekins from the hot water and serve immediately with a dollop or cream or serve the cream on the side.
To make the Brown Sugar Whipped Cream combine the cream, brown sugar, and vanilla in a small bowl and whip on high until the cream forms soft peeks. Keep covered in the fridge until ready to serve.