Preheat the oven to 300 degrees F.
Place the brioche on a baking sheet and bake in the oven until warmed through but not hard, about 10 minutes. Remove from the oven and cut the top 1/3 from each brioche. Cover with aluminum foil to keep warm.
In a large skillet or saute pan, melt the butter and oil over medium-high heat. Add the shallots and garlic, and cook, stirring, until soft, 1 to 2 minutes. Add the mushrooms, salt, and pepper, and cook, stirring, until the mushrooms are wilted and start to give off their liquid, about 4 minutes. Add the Madeira and cook, stirring, until the liquid is reduced by half, about 3 minutes. Add the veal stock and bring to a boil. Simmer, stirring, until reduced by half and thickened, about 5 minutes. Add the cream and lemon juice, and cook until reduced and thickened, about 3 minutes. Add the chives, Essence, tarragon and parsley, stir well, and adjust the seasoning, to taste. Remove from the heat.
Place 1 brioche on each of 6 plates. Spoon the mushroom mixture into each brioche and top with the brioche lid. Arrange the enoki mushrooms decoratively on the plates and serve immediately.
Yield: 6 servings