In a large sauté pan heat 2 tablespoons of oil over medium heat. Sauté the garlic and shallot until golden, about 2 minutes. Add mushrooms and sausage and cook until the mushrooms release their liquid. Continue to cook until the liquid has evaporated. Season to taste with salt and pepper.
Preheat your grill or broiler to medium high heat. Brush the baguette slices with the remaining olive oil and grill on each side until nicely browned and crisp, about 8 minutes.
Top the warm baguette slices with mushrooms and serve