Mexican chileatole is a traditional soup thickened with masa (ground nixtamalized corn). Made with fresh green chilies, the dish is called chileatole verde; with dried red chilies, chileatole rojo. This version of chileatole rojo with mushrooms comes from Friend of Milk Street, Iliana de la Vega, Mexico City native and chef of El Naranjo restaurant in Austin, Texas. Dark, raisiny ancho chilies and spicy, smoky chipotles, plus onion, garlic and tomatoes charred in a pan on the stovetop and blended until smooth, form a base for a soup with seductively deep, rich and earthy flavors. Masa harina—masa in flour form—is the thickener; it’s sold in most supermarkets with the baking ingredients or in the international aisle. If masa harina is not available, corn tortillas torn into small pieces work, too, but be sure to use corn tortillas, not those made with a blend of corn and wheat flour.