It's made with either escarole (scarole in French) or curly endive (salade frisée) and vinaigrette. Vinaigrette is a tablespoon of Dijon mustard, a tablespoon of wine vinegar, salt and pepper, and about three tablespoons of oil — good olive oil or something more neutral like canola oil.
Start by tossing the lettuce in the vinaigrette and letting it "cook" or wilt down for 10 or 15 minutes. Tough lettuces like scarole and frisée benefit from that wilting. It tenderizes them.
Meanwhile, fry some smoked pork lardons, or some thick-sliced streaky bacon cut into small pieces. When they are done, add them to the salad and toss it all around again. If there isn't already too much oil in it, a teaspoon or two of the bacon fat is good mixed into the dressing.
Then poach some eggs. Two per person if you are eating the salad as a main course, or one per person if the salad is a starter leading up to a main course in a bigger lunch or dinner. Other types of salad greens you can use are dandelion greens or Belgian endive. And some toasted croutons rubbed with garlic wouldn't be bad either.