Brown Chicken Stock:

2 tablespoons extra-virgin olive oil 
3 1/2 pounds chicken wings, backs, and bones
3 carrots, coarsely chopped
2 onions, coarsely chopped
4 ribs celery, coarsely chopped
2 tablespoons tomato paste 
1 tablespoon black peppercorns
1 bunch parsley stems

In a large, heavy-bottomed saucepan, heat the oil over high heat until
smoking. Add all the chicken parts and brown all over, stirring to
avoid burning. Remove the chicken and reserve. Add the carrots,
onions, and celery to the pot and cook until soft and browned. Return
the chicken to the pot and add 3 quarts of water, the tomato paste,
peppercorns, and parsley. Stir with a wooden spoon to dislodge the
browned chicken and vegetables bits from the bottom of the pan. Bring
almost to a boil, then reduce heat and cook at a low simmer until
reduced by half, about 2 hours, occasionally skimming excess fat.
Remove from heat, strain, and press on the solids with the bottom of a
ladle to extract out all liquids. Stir the stock to facilitate cooling
and set aside. Refrigerate stock in small containers for up to a week
or freeze for up to a month.