Preheat oven to 375°F. Butter and sugar the ramekins.

In a small saucepan, melt 2 tablespoons of butter over medium heat. Stir in the flour and cocoa powder; cook for 2 minutes.

Gradually whisk in the milk and cook, stirring constantly, until the mixture is thickened, about 4 minutes. Remove from heat.

Stir in the melted chocolate chips. Let the mixture cool slightly before adding the egg yolks, one at a time, stirring well after each addition.

With an electric mixer, beat the egg whites and salt until soft peaks form.

Gradually add 4 tablespoons of sugar, and continue beating until stiff peaks form.

Gently fold one-third of the meringue into the chocolate mixture to lighten it. Then gently fold in the remaining meringue until no white streaks remain.

Fill the prepared ramekins with the mixture. Level the tops with a knife.

Bake in the preheated oven for 18 minutes, or until the soufflés are puffed and have a slight jiggle in the center.

Serve immediately.