Preheat oven to 300 degrees.
Remove stems from pumpkins and cut off tops. Hollow out pumpkins,
discarding seeds, reserving pulp, and leaving 1/4-inch perimeter of pulp in
shells.
Cut pumpkin pulp into cubes and place in a saucepan. Cover with water
and bring to a boil. Cook until pumpkin is tender, about 20 to 30 minutes.
Drain pumpkin and place in a food processor. Purée until very fine, and
strain. Reserve 3/4 cup pumpkin pulp for this recipe and refrigerate remainder
of pulp for another use.
Combine milk, cream, 2 tablespoons sugar, cinnamon, nutmeg, and vanilla
bean in a saucepan. Bring to a boil, stirring occasionally. Remove from heat
just after mixture has come to a boil. Remove vanilla bean and add pumpkin
purée. Stir until ingredients are combined and allow mixture to cool.
Combine 2 tablespoons sugar and egg yolks and beat until eggs are pale
and form a light ribbon. Add a third of milk-pumpkin mixture to egg-yolk
mixture and beat to combine. Return ingredients to saucepan and cook over very
low heat, stirring, for 2 minutes. Be careful not to let mixture come to a
simmer.
Beat the sauce for 1 minute, off heat, to cool, and strain through a
fine sieve.
Spoon custard mixture into pumpkin shells. Place shells on a baking
sheet and bake for 45 minutes to 1 hour, or until custard has set. Remove from
oven and allow to cool on baking sheet.
Preheat broiler.
Combine white sugar and brown sugar mix. Spoon sugar mixture over
custards. Place pumpkin shells under broiler and broil until sugar has
caramelized. Check broiler after 2 minutes and turn pumpkin shells if sugar
appears to be browning only in one spot.
