Heat the oil in a large skillet over medium heat. Add the mushrooms and garlic and cook until the mushrooms have given up all their liquid and are beginning to brown. Add the onions, shallots and fennel. Cook, stirring, until all the vegetables are softened, about 5 minutes more.
Add the wine and cook, scraping the bottom of the pan to dislodge any browned bits. Let simmer until the liquid is reduced by half.
Stir in the cream. Slowly stir in the cheese, stirring until melted. Cook until bubbling and smooth, about 5 minutes. If too thick, add a little more cream or some milk.
While the sauce is cooking, toast the bread. Place 2 slices of toast on each of 2 plates and spoon the mushroom mixture over top. Garnish with the fresh herbs.