This warm salad of new potatoes, green beans, and endive, served topped with fried bacon, onions, and egg, is a Belgian specialty. Hearty and comforting, it's a complete meal in a bowl.
Set up a steamer basket inside a pot and fill the pot with water, making sure the water doesn't touch the bottom of the basket. Bring the water to a boil and steam the potatoes until tender, for 15-20 minutes. Drain and set aside.
Meanwhile, bring a large pot of salted water to a boil over high heat. Blanch the haricots verts for 2 minutes, then drain and set aside.
Arrange the endive leaves with tips pointing upward around the edge of a large serving bowl and place the mâche in the bottom of the bowl.
In a nonstick skillet or frying pan, melt the butter and sauté the bacon until golden brown. Add the onion and sweat, uncovered, for 3 minutes. Add the vinegar and bubble for 1 minute, stirring and scraping the bottom of the pan with a wooden spoon to deglaze.
Add the potatoes and haricots verts to the pan and season with pepper, to taste. Pour the warm mixture over the salad leaves, top with the chopped eggs, and serve immediately.