Butter 6 ramekins and line with a disk of parchment paper, and then butter the parchment. In a double boiler, bowl or saucepan, very gently melt the butter and chocolate together over a water bath. In a separate mixing bowl, beat the eggs and sugar until thick, pale, and ribbony. Beat in the flour, and finally the chocolate mixture. Pour the mixture into the ramekins and chill.
Just before serving, preheat the oven to 400 degrees F.
Place the ramekins on a baking sheet, and bake until the top is set, 12 to 14 minutes. Remove. Let sit 5 minutes, before unmolding onto plates. Serve with caramel sauce, if using, or a scoop of ice cream.
For the caramel sauce:
Add a spoonful of water to the sugar in a saucepan over medium-high heat and boil to caramel, about 5 minutes. Do not stir with a spoon. Swirl the saucepan over the heat until desired color is achieved. Cook's Note: Be careful not to let it get too dark. Stir in the butter to melt (careful it will splatter), then the cream. Add a squirt of lemon juice, to taste.