Step 1

Combine all ingredients and 3 quarts cold water in a large stockpot. Bring to a boil; reduce heat and simmer gently, skimming the surface occasionally, until stock is reduced by one-third, 2 1/2-3 hours.

Step 2

Strain stock through a fine-mesh sieve into a large bowl; discard solids. DO AHEAD: Stock can be made 3 days ahead. Let cool completely, then cover and chill, or freeze for up to 3 months.