By savory gelee do you mean the topping? Oysters Rockefeller is a very specific dish from Antoine's in NOLA and is served set in salt, and smothered with a compound butter. There's nothing en gelee about it that I can think of.
As a specific dish it's a bit schizophrenic in that almost everyone makes it with spinach (NOT watercress), except Antoine's (which does NOT make it with watercress either). The Antoine's recipe is a secret, but it's been extensively reverse engineered -- by me, among others.
Oysters Rockefeller in the Style of Antoine's
Serves 4 for appetizers, or 2 for over-indulging.
1 cup butter, softened
3/4 cup bread crumbs made fresh from French, Italian or other mildly sour white bread.
1/2 cup fresh chopped parlsey
1/4 cup, plus 2 tbs garlic chives, chopped; or same amount of fresh scallions, green and white parts, chopped
2 tbs fresh chopped tarragon
2 tbs fresh chopped chervil (if chervil is unavailable, substitute 1 tbs cilantro, plus a pinch of rubbed, dried sage)
1/2 tsp fresh dill
2 oz Pernod, Herbsaint, Ouzo, Arakis, etc.
Trappeys, Crystal or Tabasco hot sauce to taste
Salt to taste
Freshly cracked black pepper to taste
3 doz fresh gulf oysters, on the shell; liquor reserved
Bag of rock salt
Chopping the herbs was a cruel hoax, the purpose only to get quantities right. Process all the remaining ingredients, excepting the salt, pepper and hot sauce into a paste in the food processor, the blender, or with a mortar and pestle, into a very soft compound butter. Taste and adjust with the hot sauce, salt and pepper. If using the first method, allow the flavors to marry at least 20 minutes before serving.
Alternatively, you can cook the herbs and other ingredients in the butter just until the color starts to darken, put through a mill, and chill. This second method is probably more authentic.
Spread the salt about 1/2" deep in two baking pans. Set half the oysters in their shells into each pan, pressing them into the salt so they are firmly seated and level. Cover with cling wrap and chill. .
Preheat the broiler, and set the oven rack or broiler pan so the oysters in their pan will be about 6" from the heat. If the broiler element is inside the larger oven, the rack will probably go in the middle slot. If the broiler is separate or below, the rack will probably go in its lowest slot.
Remove one tray of oysters from the refrigerator and distribute oyster liquor among them, about 1 tsp each. Then do the same with the compound butter, about 1 heaping tbs each. Place the oysters under the broiler.
Broil until the butter melts and bubbles, and the oysters' edges curl. Serve immediately, 9 oysters per person to start. Drink much booze, preferably Sazerac cocktails. Repeat as long as you can stay standing.
Each combination of 2 dozen Rockies and 6 Sazeracs comes with a must get sick and/or lots of Mardi-Gras beads guarantee. Don't ask.
Hope this helps,