Dump everything into a large stockpot, and bring to the boil.
Once it's boiling, reduce the heat to low, give the pot a stir, cover with a lid, and allow to simmer for 1-2 hours, depending on how strong you want your broth to be.
Once the broth is done, carefully strain it into a suitable lidded container. Set aside to cool, then keep in the fridge for a week or so, or in the freezer for up to three months. (note 2)
Depending on which vegetables and herbs you use, your broth may be strong or mild-tasting. If you want a strongly-flavoured broth, use less water - weaker, use more. This recipe is for the middle ground.
If I'm not freezing my vegetable broth, and not using it straight away, I keep it in 1-litre clip-top bottles or jars.
I don't add salt or pepper to my veggie broth because I prefer to add seasonings to the dish itself, not the broth; however, if you'd rather add it to yours, go ahead.
Nutritional data is based on using leek, carrot, red pepper, celery, parsnip, potato, onion, cabbage, and cauliflower scraps, plus half a bulb of garlic.