Decide your cooking style: braise/soup (needs wilt-tender leaves) or salad (needs crisp-tender bite).
Choose the substitute with the closest texture first: endive for closest bitterness/leaf feel, romaine for crisp-tender, radicchio/kale for stronger leaf character.
Use the listed ratio; if your substitute is naturally more bitter (like radicchio), start with less than escarole.
Adjust bitterness and balance: add a small splash of lemon/vinegar (or a pinch of sugar) to match escarole’s mild tang.
Adjust cooking time: romaine wilts faster than escarole, while kale needs more time; test tenderness before serving.