In a small saucepan, bring the chicken stock and the dried porcini to a simmer over moderate heat. Remove the saucepan from the heat and let the chicken stock stand.
In a large skillet, melt the butter in 1 tablespoon of the olive oil. Add the chopped shallot and cook over moderate heat until the shallot is softened, about 4 minutes. Add the mushrooms, season with salt and pepper and cook over moderately high heat until tender, about 6 minutes.
Remove the porcini pieces from the stock, coarsely chop them and add them to the fresh mushrooms along with the garlic paste. Add the sherry and cook until reduced by half, about 1 minute. Pour in the porcini stock, stopping before you reach the grit at the bottom, and simmer the mushroom stew until it is reduced by half, about 5 minutes.
In a large nonstick skillet, heat the remaining 1 tablespoon of olive oil. Add the fish, season with salt and pepper and cook over moderately high heat for 2 minutes per side. Add the fish to the mushroom stew and cook for 1 minute. Add 1 tablespoon of the chives and season with salt, pepper, Worcestershire sauce and hot sauce. Garnish with the remaining 1 tablespoon of chopped chives and serve at once.