Preheat the oven to 450°F (230°C).
In a skillet over medium-high heat, heat the oil, then add the onions and all three types of mushrooms, and cook, stirring, for 6 minutes. Add the garlic and cook for 2 minutes, stirring frequently. Deglaze with the cognac (if using) and bring to a boil while stirring, then lower the heat and simmer for 1 minute.
Stir in the broth, sage, salt, rosemary, garlic powder, basil, mustard, pepper, and maple syrup. Bring to a boil, then lower the heat and simmer, stirring frequently, until the liquid is fully absorbed, about 5 minutes. Stir in the soy cream and cook for 1 minute.
Divide the mushroom mixture among 4 ramekins set on a baking sheet. Sprinkle vegan cheese over each ramekin, dividing evenly.
Bake for 10 minutes, or until the cheese is melted and golden brown. Serve with toast.