Step 1

Heat the oven to Cut the mushrooms roughly into pieces the size of a quarter, then toss with the oil, and vegetables, lay out in a single layer on a baking sheet, and roast for 60 minutes, or until dried out and beginning to color.

Step 2

Check on the mushrooms at 30 minutes to shake the pan and check on them—if the heat seems too hot, turn it down, since if the mushrooms burn it can ruin the stock. You want to take your time here, leisurely roast them and dry them out, and opposed to roasting them hard to caramelize them. Keep in mind that your woody trim and scrap will have less water weight than typical fruiting bodies or tender margins of the same mushroom, so they may dry out and start to color slower or faster depending. Use your instincts.

Step 3

Take the roasted mushroom mix and put it into a stock pot with the fresh herbs, add the water until it barely reaches the top, bring it to a simmer, then turn the heat down to low and cook for 2 hours with the lid ajar. Strain the liquid, whisk in the salt if using, cool, and refrigerate. The stock will keep for at least a week if not longer, especially if you add the salt, and can be frozen.