Pre-heat your grill to 375F, according to manufacturers instructions.
Melt the chocolate in a large bowl over a double boiler, or in the microwave. Set aside to cool a bit.
Prepare four ramekins, by brushing with melted butter and then sprinkling with granulated sugar to coat the inside. Shake out any excess sugar.
In the bowl of a stand mixer with the whisk attachment, or bowl with a hand mixer; add the egg whites and and pinch of salt, and whip the egg whites until frothy. Continue to whisk while slowly streaming in the 1/3 cup of sugar. Whisk until the egg whites form soft glossy peaks.
Add the egg yolks to the cooled melted chocolate and stir. You can pass the through a strainer to do this if there are large bits of egg white still attached. The chocolate and yolk mixture will thicken a bit.
Mix 1/3 of the egg white mixture into the chocolate and yolk mixture to lighten up the base. Then fold in the remaining egg whites in two additions. The mixture should be smooth but does not have to be fully incorporated. You don’t want to overmix, and deflate the eggs.
Spoon or use a piping bag to fill the ramekins. Run your thumb around the inside of each ramekin to help them rise more evenly.
Place the ramekins on a sheet pan, on the grill grates and cook for 20-25 minutes until the soufflés have risen and the center is set.