How to Make It
Put the lentils in a small saucepan, cover with 1 inch of water and bring to a boil. Simmer over low heat until tender, about 20 minutes.
In a small bowl, combine the olive oil with the red wine vinegar and season with salt and pepper. Drain the lentils and return them to the saucepan. Add 2 tablespoons of the vinaigrette, season with salt and pepper and toss the lentils well. Cover and keep the lentils warm.
Using a mandoline or a vegetable peeler, thinly slice the parsnip lengthwise into strips. In a large skillet, heat 1/2 inch of vegetable oil until shimmering. Add one-fourth of the parsnips to the oil at a time and fry over moderate heat until browned, about 1 minute. With a slotted spoon, carefully transfer the parsnips to paper towels to drain. Lightly season the fried parsnips with salt.
Pour off all but 1 tablespoon of the oil in the skillet and heat until shimmering. Season the duck breasts with salt and pepper, add them to the skillet and cook over moderately high heat until nicely browned outside and medium-rare within, about 4 minutes per side. Transfer the duck breasts to a carving board and let rest for 5 minutes.
In a large bowl, toss the mesclun greens with the lentils. Thinly slice the duck breasts crosswise. Add the duck to the salad along with the remaining vinaigrette and toss well. Add some of the crisp parsnips to the salad and carefully toss again. Transfer the duck salad to a platter, top with the remaining fried parsnips and serve right away.