In a skillet, heat oil over medium high heat for 30 seconds. Add beef and onions and cook, stirring, until beef is no longer pink, about 5 minutes. Add garlic, toasted cumin, oregano, salt, peppercorns and cinnamon stick and cook, stirring, for 1 minute. Add diced tomatoes with juice and bring to a boil.
Place squash and beans in slow cooker stoneware and cover with sauce. Cover and cook on Low for 6 to 8 hours or on High for 3 to 4 hours, until squash is tender.
Half an hour before recipe is finished cooking, in a heatproof bowl, soak dried chile peppers in boiling water for 30 minutes, weighing down with a cup to ensure they are submerged. Drain, reserving 1/2 cup of the soaking liquid. Discard stems and chop coarsely. In a blender, combine rehydrated chiles, cilantro and reserved soaking liquid. Puree. Add to stoneware and stir well. Cover and Cook on High for 30 minutes, until hot and bubbly and flavors meld.
TIP: If you prefer, you can soak and puree the chilies while preparing the chili and refrigerate until you’re ready to add them to the recipe.
MAKE AHEAD: This dish can be partially prepared before it is cooked. Complete Steps 1 and 3. Cover and refrigerate tomato and chile mixtures separately overnight. The next morning, continue with the recipe. Serves 6.