Roasted Mushroom Stock

Name: Roasted Mushroom Stock
Ingredients: 1 1⁄2 lb. (680 g) cremini mushrooms, including stems; 1⁄2 lb. (225 g) white onions, cut into small dice; 1 lb. (455 g) leeks, dark green parts removed, cut into small dice; 1⁄2 lb. (225 g) carrots, cut into small dice; 1⁄2 lb. (225 g) parsnips, cut into small dice; 1⁄2 small fennel bulb, coarsely chopped, fronds removed; 1⁄2 head garlic, unpeeled; 3 tbsp. grapeseed oil; 1 tbsp. dry vermouth (optional); 2 sprigs marjoram; 4 sprigs flat-leaf parsley; 12 black peppercorns; 2 bay leaves; Sea salt to taste