This hearty ragu straddles the line between sauce and stew. All the ingredients—from the cremini mushrooms to the warm spices to the crushed tomatoes—combine for an amazing depth of flavor in the braise. Green olives, added both at the beginning and end of cooking, add a wonderful briny undertone that balances the ragu’s richness. Look for Castelvetrano olives, which are firm and meaty; they are sold in jars, or check the olive bar in the deli department. If not available, use any large jarred green olive; avoid canned olives, which tend to be soft and taste metallic. Toss the ragu with a chunky pasta shape such as ziti, spoon it over polenta or simply offer warm, crusty bread alongside. However you serve it, offer grated Parmesan cheese for sprinkling at the table.