In a large, deep skillet or pan with a lid, sauté the onion, fennel, garlic, and anchovy in butter/olive oil until the onion starts to soften and the anchovy breaks up. Add the potatoes in a single layer.
Add remaining ingredients, cover, and bring to a boil. Cook for about 10 minutes or until the potatoes are tender.
Uncover, reduce heat slightly and continue to cook until the liquid has evaporated about 10-15 minutes. Continue to cook until the potatoes brown on the bottom to your taste.
Serve with leftover fronds if desired.