Peel and cut the carrot chunks, quarter the onions, and toss them in a bowl with a little oil and sprinkle of salt and pepper.

Pre-heat the oven to 400 degrees and roast the carrots and onion for about 45 minutes until they are beginning to brown.

Cut the celery stalks into 3 or 4-inch lengths, and cut the zucchini into chunks and toss with a little oil, salt and pepper, along with the whole mushrooms. Stir these into the roasting pan and continue cooking for another 45 minutes or so.

Finally, lightly bash the Garlic cloves to help them release their flavor, add them to the pan, and roast for another twenty minutes until everything is nicely caramelized.

Deglaze the pan with a half-cup of water and add this to the stock-pot along with the vegetables once they have cooled.

Add 8 cups (2 liters) of cold water to the pot and simmer gently for about 4 hours.

Strain out the vegetables and then reduce the stock to about half its original volume by boiling.

Cool and refrigerate or freeze for later use.