Preheat the broiler. Lightly butter the insides of 4 large ramekins and place on a baking sheet. Set aside. In a large skillet or saute pan, combine the scallops, onion slices, lemon slices, bay leaf, wine, and water. Bring to a simmer and gently poach the scallops until just firm, about 3 minutes. Remove with a slotted spoon. Strain the scallop cooking liquid into a clean container. Reserve the scallops on a plate.
In a clean large saute pan or medium saucepan, melt 1 tablespoon of the butter over medium-high heat. Add the shallots and garlic, and cook, stirring, for 30 seconds. Add the mushrooms and cook, stirring, until tender, about 4 minutes. Remove with a slotted spoon.
Add the remaining 2 tablespoons of butter to the pan the mushrooms were cooked in and melt over medium heat. Add the flour and cook, stirring constantly for 2 minutes, to form a light roux. Slowly add the strained poaching liquid, whisking constantly, and cook until thick, about 2 minutes. Add the milk, lemon juice, salt, pepper, and cayenne, and whisk well. Bring to a boil and cook for 1 minute. Add the parsley and green onions, and simmer for 1 minute. Add the cream and Gruyere, stir well, and remove from the heat. Fold in the scallops and mushrooms, and pour into the prepared ramekins.
In a small bowl, combine the bread crumbs, butter and Essence. Sprinkle over the scallop mixture and top with the Parmesan. Run under the broiler until just crisp and brown, being careful not to overcook, 1 to 2 minutes. Remove from the heat and serve immediately.
Essence (Emeril's Creole Seasoning):
Yield:about 2/3 cup
Combine all ingredients thoroughly and store in an airtight jar or container.
Recipe from "New New Orleans Cooking", by Emeril Lagasse and Jessie Tirsch. Published by William and Morrow, 1993.