As you cook throughout the week, freeze vegetable, herb and fruit scraps in a large ziplock bag, omitting any bad or mouldy spots. Make sure to include your garlic peels and onion skins. Some example scraps: broccoli and cauliflower stalks, carrot, beet and sweet potato peels, parsley and cilantro stems, apple and pear peel.
Heat oven to 400°F.
Toss the frozen vegetable, herb and fruit scraps with the olive oil, until gently coated.
Place the scraps on a foil-lined baking sheet and roast for about 20 minutes, turning them at least once halfway.
Place the roasted scraps in a large pot, scraping all the roasted brown pieces into the pot as well.
Cover with water. A good rule of thumb is 1 cup of water per cup of scraps for a very flavourful stock; you can always dilute it to taste when using in a recipe.
Bring to a boil.
Once boiling, reduce heat to a simmer. Loosely cover (with the lid cracked).
Simmer for at least an 1 hour; the flavour will deepen the longer it cooks.
Using a fine mesh strainer, remove the scraps from the broth, pressing down on solids to extract as much liquid as possible. Discard the solids.
Use immediately to make soup, or freeze in small portions for easy use in day to day cooking.