A 6- or 8-cup enameled cast-iron casserole is ideal here because it allows the whole operation to take place in one vessel. But if you don’t have such a utensil, you may caramelize the sugar in a heavy-bottomed skillet and then transfer it to a heat-proof casserole or soufflé dish of the proper dimension.
• 1/2 cup sugar
• 2 tablespoons water
• 2 1/4 cups light cream or half-and-half
• 4 eggs
• 2 egg yolks
• 1/2 cup Morning Glory Old Fashioned Coffee Syrup (made in S. Dartmouth MA)
• 1 tablespoon rum (optional)
Preheat the oven to 325 degrees, and find a baking pan which will accommodate your flan mold as a water-bath with at least an inch to spare all around. Fill your tea kettle with water and bring to a boil for later.
Put the sugar in a heavy casserole or skillet as specified above. Place over medium heat. Cook without disturbing very much until sugar melts and begins to caramelize and darken. Watch carefully. Use a wooden chopstick to stir it only if it darkens unevenly or hard lumps of sugar remain unmelted. When the syrup is deep amber throughout, turn off the heat and, using pot holders, pick up the casserole and swirl the syrup to coat the sides. (If you are using a separate mold, pour the syrup in and swirl instantly to coat it. Preheating the mold in the oven for a few minutes before adding the syrup is helpful. In any event, remember that caramel is very hot and exercise caution.) Set prepared mold aside to cool while you make the custard.
In a medium bowl, whisk the eggs and egg yolks together just until homogeneous. Whisk in the cream and the coffee syrup. Pour this mixture through a sieve into the prepared mold. Place the mold in the baking pan, and add hot water to the baking pan up to the level of the custard in the casserole. Carefully place in the oven. (Alternatively, you may put the arrangement in the oven, and then add the water carefully.)
Bake 70 minutes, and then check for doneness by wobbling gently. If it seems set, insert a thin knife into the custard near the center to see whether it emerges clean. (It is ideal to remove the custard from the oven when it is fully set an inch or so from the center, but still pretty wobbly. It will continue to cook after it comes out of the oven, especially if it’s in a heavy mold.) If you have an instant-read thermometer, let it eliminate the guesswork for you: 165-170 degrees F in the center.
Remove the custard from its bath and allow to cool to room temperature. Cover and refrigerate at least 8 hours.
To unmold, run a small knife around the perimeter, just to make sure it’s free. Warm the bottom of the mold briefly either over low heat (if it’s metal) or in a boiling water bath (if it’s ceramic or glass). Invert onto a serving platter with a lip. Some syrup will remain in the mold. Place over low heat with a tablespoon or two of water (or rum), and swirl until dissolved. Add to serving dish.