Make the batter: Melt 4 tablespoons of butter and the chopped chocolate together in a large heatproof bowl in the microwave (or a double boiler, if you have one). Microwave in 20 second increments, stirring after each until completely melted and combined. Slightly cool for 3-5 minutes.

Then whisk your egg yolks, vanilla extract, and salt into chocolate mixture. Set aside.

In a completely CLEAN residue-free medium glass or metal mixing bowl (wipe down with a bit of vinegar to be sure), use a handheld mixer or stand mixer fitted with a whisk attachment to beat the egg whites and cream of tartar together on high speed until soft peaks form. This should take about 2 minutes.

Then with the mixer running on high speed, slowly add the sugar in three separate additions, about 1 tablespoon at a time, beating for 5 seconds before adding the next tablespoon.

After all 3 tablespoons of sugar have been added, beat until stiff glossy peaks form, about 2 more minutes. Do not over-beat.

Slowly and GENTLY fold the egg whites into the chocolate mixture a bit at a time. The goal here is to not lose the air out of your whipped egg whites, because that's where the souffle's rise will come from. It’s best to do this in 3 separate additions (starting with a small one where you can be a little rougher and kind of "slacken" the mixture to make it easier to stir in), combining each addition completely before folding in more.

Refrigerate the batter for 5-10 minutes as you preheat the oven and prepare the ramekins. (If leaving in the fridge longer in than an hour, cover it; you can make this up to two days ahead of time).

Prepare the ramekins: Adjust the oven rack to the lower third position and preheat to 400°F (204°C).

Brush a generous coating of the softened butter all over the inside of four 6-ounce oven-safe straight sided ramekins. Sprinkle in the granulated sugar, then shake/rotate each to ensure every spot of the ramekin has a sugar coating (discard the excess). Place ramekins on a baking sheet.

Spoon your batter evenly into the ramekins. It should come right to the top, then using a knife or icing spatula, smooth the surface flat. Run the knife/icing spatula (or even your thumb) around the rim at the top to create a little “channel” between the batter and the rim of your pan (see pics).

Bake:  Place the baking sheet with your ramekins in the oven. Close the door and immediately reduce the temperature to 375°F (191°C). Bake for 13 to 14 minutes, or until the edges are set and the center just barely jiggles when you give the pan a light tap. Don't open the door at all until at least after 10 minutes, but avoid opening much at all.

Remove from the oven and serve immediately (plain or with optional toppings). Soufflés begin to fall within minutes so you want to serve them fresh.