Spoon the batter into the prepared mold. (The mold should be about two-thirds full.) Set the prepared circle of parchment or wax paper, sprayed-side down, on top. Cover with the lid or a double thickness of foil, securing with string or masking tape. Set the mold in the pot and pour in enough boiling water to come halfway up the sides of the mold. Bring the water to a simmer; reduce heat to low, cover the pot and steam the pudding for 2 hours. (Add more water to maintain level during steaming, if necessary.) The top of the pudding should spring back when touched lightly, and the sides should pull away slightly from the sides of the mold. Transfer the mold to a rack, uncover and let stand for 10 to 15 minutes before unmolding.