Slice the oyster mushrooms into 1cm strips. Melt 2 tablespoons of the vegan margarine in a shallow casserole pan over a medium-high heat, then add the mushrooms, stir in the chicken seasoning and fry for 15–20 minutes, or until the mushrooms are crispy. Remove from the heat, spoon the mushrooms on to a plate and keep to one side.
Meanwhile, peel and chop the shallots and garlic. Melt the remaining tablespoon of vegan margarine in the pan, reduce the heat to medium, then add the shallots and garlic. Fry for 4 minutes, stirring occasionally.
Stir in the flour and fry for 2 minutes, then very slowly pour in the wine, stirring quickly to prevent the flour clumping together and using the wine to deglaze the pan, gathering up as much flavour as possible. Simmer for 1–2 minutes, then stir in the stock, mustard and herbes de Provence. Trim the ends off the green beans and add them to the pan.
Simmer for 10 minutes, until the beans are cooked but still have a good bite left to them.
Meanwhile, chop the chives and pick the parsley leaves from their stalks, then roughly chop the leaves. Add the cooked mushrooms, most of the parsley leaves and the vegan single cream to the pan, and cook through for 1–2 minutes. Season to taste with salt and pepper.
Top with the chopped chives, the remaining parsley leaves and freshly ground black pepper, and serve alongside the sliced baguette.
Tip: If you want to avoid using the white wine, simply substitute 2 teaspoons of apple cider vinegar.