To make the stuffed chiles, roast, peel and seed the chiles, keeping them whole for stuffing. Set aside. Heat the oil in a large skillet over medium heat and saute the onions about 4 minutes, until translucent. Add the ground lamb and brown 15 minutes, stirring occasionally to prevent burning. Drain off the excess fat and add the bread crumbs, tomatoes, garlic, salt, pepper, and herbs. Decrease the heat and simmer another 15 minutes. Remove from the heat and let cool. Slice the chiles lengthwise, spread them open on a work surface and generously stuff each chile with the lamb mixture. Place the stuffed chiles on an oiled baking pan with the open side down and set aside.

To make the puree, heat the oil in a saucepan over medium-low heat. Add the garlic and saute for 1 minute. Add the tomatoes and cook another 15 minutes, stirring occasionally to prevent burning, until the excess liquid evaporates. The sauce will reduce and thicken. At this point you can pour the sauce through a fine sieve to remove the skins or you can serve the sauce as it is. Set aside.

Preheat the oven to 350 degrees F. Place the stuffed chiles in the baking dish in the oven and heat until hot, about 5 to 10 minutes. Serve immediately with the tomato puree. Garnish with sour cream, if desired.