Wash the greens and spin them dry. Fry the bacon in a sauté pan or wok until crisp, about 5 minutes. Deglaze the pan with the vinegar and boil to reduce to about 2 teaspoons. Add enough oil to make a dressing. Toss the greens in the pan for a few seconds just to coat– don’t let them wilt. Divide among four plates and season with fleur de sel and freshly ground pepper.
*If you like, make goat cheese croûtes to serve alongside. Simply smear goat cheese on slices of baguette. Drizzle over olive oil. Grind on pepper. Pop them in an oven at about 400°F/200°C until the bread has toasted and the cheese is very hot.