Preheat the oven to 400 degrees. To a large skillet over medium-high heat, add 2 tablespoons of the olive oil. When the oil is hot, add the garlic cloves. Once the garlic is sizzling, add the mushrooms and sage, and cook, without stirring, until browned on one side, about 2 to 3 minutes. Stir, and brown the other side. Season with the salt, cover, and cook until tender, about 5 minutes. Uncover, remove the garlic, stir in the parsley, and set aside.

On a baking sheet, brush the lightly toasted bread on both sides with the remaining 2 tablespoons olive oil. In a medium bowl, toss together the grated cheeses. Stir half of the cheese mixture into the mushrooms.

Spread the mushroom mixture on the toasts, and sprinkle with the remaining grated-cheese mixture. Bake until the tops are browned and the cheese is bubbly, about 10 to 12 minutes. Serve hot.