Try making your own stock from Roasted Veggies for flavor and Lots of Bones...especially Femur bones (get them at your butcher). Bones naturally contain gelatin. After making your stock reduce it by 50% the gelatin contained in the stock will thicken the sauce naturally...or try that thing that Phill said it makes sense...
Here's a great hardy stock recipe that I wrote recently for the cooking deficient.
While I cook through out the week I end up with a tupperware full of scraps. Chicken or Turkey Bones, Onion ends, celery ends, herb stems, mushroom bottoms. Things that most people would throw away. Most of these things can be used to produce a super hearty stock. Usually I save up my Turkey Bones for a few weeks in the freezer.
Tools & Ingredients:
Large Stock Pot
Ladel for skimming
Wire mesh strainer
Containers for Cooling and Storing
Turkey or Chicken Bones (or beef femur bones)
Wholesome Vegetable Trim (any of these)
(leeks, onions, carrots, celery, parsnips, turnips, tomatoes, mushrooms)
Aromatics (any of these)
(herb stems, bay leaves, citrus fruits, peppercorns, dried spices)
1. Preheat oven to 400. Toss all bones with olive oil and put into a large roasting pan sprayed with non stick spray. Roast for aprox 45min till they have a nice rich dark color, turning half way through.
2 Pour some water into the roasting pan and scrape off all the brown bits from it. That's the good stuff!
Put all vegetable into the stock pot with a touch of olive oil and saute lightly while your bones are roasting.
Add all your spices, bay leaves, peppercorns, citrus fruits, and herb stems to the stock pot.
Add your roasted bones and liquid from scraping the roasting pan into the stock pot.
Fill with cool water to cover all the items in the pot.
Bring to a boil then turn down to a simmer.
Simmer lightly for about 3-6 hours (if using beef bones you can simmer up to 10 hours). The fat will seperate from the stock after about 1 hour of simmering. Skim the top with a ladel to get most of the fat out of the stock.
Let the stock cool slightly then strain it out into containers. You can add ice at this point to cool it quicker.
This stock can be used for braising meats to make a hearty stew or soup and also to make incredible sauces by reducing and adding your favorite herbs or flavor pastes.