Preheat oven to 325 degrees F.

Cut tops off pumpkins and reserve. Using a spoon, scoop out seeds and discard. Brush cavities with butter and sprinkle evenly with 2 tablespoons of the sugar. Replace lids and place pumpkins in a roasting pan. Cook 35 minutes, or until flesh is tender. Let cool.

When cool enough to handle, use a sharp knife to cut out flesh from insides and lids of each pumpkin. Remove about 1/4 cup flesh from each and reserve, leaving cavities evenly shaped. Sprinkle cavities evenly with 2 tablespoons of the sugar. Sweeten pumpkin flesh with remaining 2 tablespoons of the sugar and mash with a fork until combined.

In a heavy saucepan combine cream and maple syrup. Bring almost to a boil over medium-high heat. In a large bowl lightly beat yolks with reserved pumpkin flesh; slowly stir in hot cream mixture. Divide custard among pumpkin shells and replace lids; return to roasting pan. Pour enough hot water into pan to reach 1-inch up sides of pumpkins. Cook 1 hour or until custard is barely set. Remove lids and reserve. Sprinkle custards evenly with brown sugar and bake 15 minutes more. Custards will be slightly runny.

Cool pumpkins 30 minutes or cool to room temperature and refrigerate until cold. Replace lids before serving.