Chop 1/3 of the pancetta into small pieces. Place pancetta in a small sauté pan over medium heat. Stir and cook until the pancetta is crisp and golden. Pour off the fat and place the pan with the pancetta back on the fire. Add the butter to the pan. When the butter begins to foam, add the leeks with some salt. Lower the heat and cover. Cook for 3 minutes until the leeks soften, then add the butternut squash and thyme. Cover for 5 minutes, remove the cover and mix the squash, butter and leeks. Cover and continue to cook until the squash is fully cooked. Remove from the heat.