If using fingerling potatoes, scrub, then halve them lengthwise. Large round potatoes can be cut into thick rounds or quartered lengthwise.

Warm the oil in a wide pot with the onion, saffron, peppers, garlic, and potatoes. Cook over medium-low heat, stirring gently every now and then until the potatoes are tender-firm, about 25 minutes. Add the paprika, parsley, and pepper flakes and cook for 3 or 4 minutes. Add the sherry and cook until the juices in the pan are thick and syrupy, about 12 minutes.

Add the tomatoes, chickpeas, and broth to cover. Season with 1½ teaspoons salt and plenty of pepper. Cover and cook over low heat until the potatoes are completely tender, about 20 minutes. If the stew is soupy and you plan to serve it right away, stir in ¼ cup picada (or more, if necessary) to thicken it. If you don’t plan to serve the stew for 1 hour or more, it may not need the bread crumbs since it will thicken as it stands. Serve in soup plates with any additional picada sprinkled over the top along with the extra parsley. Add a spoonful of the Romesco sauce to each bowl and pass the rest.