1. Heat the oil in the cooker and saute the onions and garlic (if using) over medium heat, stirring frequently, until golden brown, about 5-6 minutes. For a richer stock of darker colour, saute the onions until dark brown, about 15 minutes.

2. Tossin the carrots and celery and saute an additional minute.

3. Add the parsnips, bay leaves, thyme or oregano, herbs, chopped vegetables, and salt, with just enough water to reach the maximum capacity advised by the manufacturer. Stir carefully to scrape up any browned bits of onion sticking to the bottom of the pot.

4. Lock the lid in place and over high heat bring to high pressure. Adjust the heat to maintain high pressure and cook for 10 minutes. Let the pressure drop naturally, about 7-10 minutes, or use a quick-release method. Remove the lid, tilting it away from you to allow any excess steam to escape.

5. Allow the stock to cool slightly. Strain into a large storage container. Cover and refrigerate until needed.

Possible vegetables for coarse chopping and inclusion in the 8 cups: potato peelings broccoli stalks zucchini celery, parsnip, and carrot chunks, peelings, and trimmings wilted celery and carrots onions, peeled leek greens scallions parsley, dill, coriander, and basil sprigs, leaves, or stems wilted lettuce and watercress turnips, peeled bay leaf or a few pinches of dried herbs