Preheat the oven to 350 F and move your top oven rack to the middle.

Chop the pancetta or bacon into bite-size pieces and begin sautéing over medium heat in a large (at least 4.5 qt) Dutch oven. Add a little olive oil if necessary to keep the pancetta from sticking.

Remove the leaves from the rosemary sprigs and chop. Add the chopped rosemary to the pan as well as the two bay leaves.

Clean and thinly slice the leeks. Mince the onion and garlic cloves.

Add the onion and leeks to the pancetta pan, continue to cook until translucent, about 10-15 minutes. Add the garlic, sauté one minute until fragrant.

While the onions and leeks cook, peel and dice the butternut squash or sweet potatoes into roughly even bite-size chunks. Gently clean the mushrooms with a cloth towel, remove the base of the stem, then chop into thirds. Remove the skin from the chicken thighs as well as any pieces of gristle.

Add the diced squash, mushroom thirds, and skinless (but bone-in) chicken thighs to the onion-leek-garlic mixture. Gently stir to distribute.

Pour in the wine or beef stock, increase the heat to bring the stew to a gentle simmer, and allow the wine to reduce somewhat (about 5 minutes) while stirring occasionally.

Add the diced tomatoes, then the pitted olives. Stir to distribute.

Transfer the Dutch oven from the stovetop to the oven, then bake about 80-90 minutes until chicken is fall-off-the-bone tender and squash/sweet potatoes are tender as well.

Season according to taste with salt and pepper, then serve.

Jamie suggests eating a bowlful together with 7 ounces of whole-grain bread (with seeds).