Lay onions, carrots, and celery on a baking sheet in a single layer. Broth extras: If using garlic or extra root vegetables, add those to the baking sheet too.
Drizzle veggies with olive oil and 1 teaspoon of salt. Roast about 30 minutes, until veggies are cooked through.
Add vegetables to a large soup pot, along with the rest of the salt and all remaining ingredients (including the reserved celery leaves).Tip: If using tomato paste, add it now.
Bring the mixture to a boil, and simmer for about 20 minutes. Strain out any solids (vegetables and herbs) from the broth.
Use broth right away, refrigerate and use within 3-4 days, or freeze broth in an airtight container for up to 6 months.
Notes
Note: For a much clearer broth, avoid bringing broth to a boil, and extend the simmer time to 3 hours.
*Nutrition Information does not includevegetables, because they are discarded and not consumed. Wine is included.