This recipe is excerpted from Dorie Greenspan's Baking Chez Moi (Houghton Mifflin Harcourt).
Center a rack in the oven and preheat the oven to 300 degrees F. Line a roasting pan or a 9-by-13-inch baking pan with a double thickness of paper towels. Have it and four 6-to-8-ounce ramekins at hand. Bring a kettle of water to a boil.
Reserve 2 tablespoons of the sugar and sprinkle the remaining sugar over the bottom of a small skillet or saucepan, preferably nonstick, and put the pan over medium-high heat. When you see the sugar start to melt around the edges, begin stirring it in small circles, making your way around the edges and then going deeper into the center of the pan, until all the sugar is melted, blended, bubbling and, most important, a medium amber color; stay with the caramel, because the color changes in seconds. You can check the color by dropping a bit on a white plate. As soon as it's the right color, pull the pan from the heat and, being very, very careful (caramel is ferociously hot and sticky), divide it among the ramekins. Hold the ramekins by their tops and swirl to coat the bottoms with caramel. You'll never get the caramel perfectly even, and that will never matter. Place the ramekins in the roasting pan.
Put the milk and the reserved 2 tablespoons sugar in a small saucepan and bring to a boil.
Put the chopped chocolate in a heatproof bowl and pour the hot milk over it. Let stand for about 5 minutes to melt.
Meanwhile, put the eggs in a medium bowl and whisk them for about 1 minute; they'll pale a bit. Using a heatproof spatula, stir the chocolate and milk together until smooth. Then, stirring the eggs without stopping, gradually pour the hot chocolate milk over the eggs and stir until blended. You'll have bubbles on top of the creme, don't worry: You're going to turn the custards over and no one will ever see the bottoms.
Divide the custard among the ramekins. Pour enough hot water into the roasting pan to come halfway up the sides of the ramekins. Carefully slide the pan into the oven.
Bake the custards for 35 to 45 minutes, or until they are firm around the edges and just jiggly in the center. Remove the roasting pan from the oven and carefully place the ramekins on a cooling rack. Leave the ramekins at room temperature for about 20 minutes, then transfer them to the refrigerator. Chill for at least 4 hours, or until they are thoroughly cold, before serving. (You can make these 1 day ahead; cover and keep refrigerated.)
When you're ready to serve, run a table knife around the edges of the ramekins, then turn the custards over onto small plates with raised rims. You might have to shake the ramekins a little or tap them gently against the plate to cajole the custards to come out, but fear not -- they won't stick.