In a small pot over medium heat, melt butter and keep warm on the side. In a bowl, whip firmly the egg yolks and the 6ounces of sugar until it becomes whiter and foamier (about 6 minutes). Pour hot butter over the chocolate, mix well with a whip until chocolate is melted and then blend with the yolks and sugar mix.
Whip 7 egg whites with the lemon juice. When they become stiff, add 1ounce of sugar. Whip for a few more minutes and then incorporate the chocolate and yolk mixture into the whipped egg whites. Gently fold the two together with a spatula to keep the preparation light and foamy. Transfer the mix into the cups.
Preheat the oven to 350°F. Place the cups in a pan of water and cook for 5 to 6 minutes. Remove and unmold onto the serving plate. The soufflés can be served with whipped cream or ice cream on the side.