Tender and delicate miniature cauliflower is often available in the fall. Serve this ragout as a side dish or over rice, or cut the cooked cauliflower into smaller pieces, and use ragout as an omelet or frittata filling.
Heat the oven to 350 degrees. Heat the olive oil in a 3-quart ovenproof casserole or pan over medium heat. Add the onion, and cook, stirring occasionally, until translucent, about 5 minutes. Add the garlic and minced anchovy fillets; cook until garlic is softened, about 3 minutes. Add the mushrooms; cook until their liquid is released and evaporates, about 5 minutes.
Stir in the tomatoes, rosemary, olives, capers, and bay leaves. Cook over medium-high heat, stirring occasionally, until all the flavors combine, about 10 minutes. Transfer half of the mixture to the bowl of a food processor, and process until it is slightly chunky; return to pan. Use a large spoon to break up larger pieces of tomato.
Arrange the cauliflower over the sauce in the pan. Cover, and cook until cauliflower is tender, about 30 minutes. (If mixture is too soupy, continue to cook another 5 to 10 minutes, uncovered, to reduce liquid.) Serve hot.
White button mushrooms can be used instead of the large cremini.