- 2 pounds red potatoes, scrubbed
- 1 large onion
- 1 tablespoon butter
- 6 tablespoons olive oil, divided
- 1 clove garlic
- ¼ teaspoon kosher salt
- freshly ground pepper
- 2 tablespoons Dijon mustard
- 1 tablespoon fresh lemon juice
- 2 tablespoons chopped fresh herbs
(parsley, chives, dill, tarragon, your choice, optional)
Cut potatoes in big bite-size chunks and cover with cold salted water in a saucepan. Cover and simmer until just tender. Drain and set aside to cool.
Peel onion and slice into thick (about ½-inch) slices, across the grain. Melt butter with one tablespoon of the olive oil in a heavy-bottomed sauté pan over medium heat. Arrange onion slices in pan and turn heat to low. Cook and brown the onions very slowly, flipping them gingerly when the time is right.
This takes more than half an hour but requires only occasional monitoring.
Make the vinaigrette:
Mince and mash together the garlic clove and salt. Grind on a good deal of pepper. In a small bowl, whisk together this mixture with the mustard and lemon juice. Whisk in remaining olive oil, in a gradual fine stream. Vinaigrette will emulsify and thicken. Whisk in optional herbs, if using.
Gently toss cooled potatoes in vinaigrette, arrange in serving dish, and top with caramelized onion wheels. Serve at room temperature.