Pick over and rinse the lentils, and put them in a 3- to 4-qt. saucepan. Pile the thyme, bay leaves, garlic, and peppercorns on a 5-inch square of double-layer cheesecloth. Gather up the edges and tie into a little pouch with kitchen twine. Add the pouch to the pan along with the onion and carrot. Fill the pan with cold water to cover the lentils by about 2 inches, and bring to a boil over medium-high heat. Immediately lower to a gentle simmer—boiling can break the lentils—and simmer, uncovered, until just tender, 30 to 40 minutes. (If the water level drops below the surface of the lentils as they simmer, add a little more water.)
Meanwhile, put the sausage in a small saucepan or deep skillet. Add the wine and enough water to cover by about 1/2 inch. Bring to a simmer. Reduce the heat as needed to cook at a bare simmer (bubbles should only occasionally break the surface), uncovered, until a metal skewer inserted into the center comes out feeling hot to the touch, 15 to 20 minutes.
While the lentils and sausage cook, make the vinaigrette: In a medium bowl, whisk 1-1/2 Tbs. of the vinegar with the mustard and a pinch of salt. In a steady stream, whisk in the olive and walnut oils. Season to taste with salt.
tip: Toss the lentils with a little salt and vinegar immediately after draining, and you'll see a big boost in the flavor of the salad. Like potatoes, lentils firm up as they cool, which slows their ability to absorb seasonings.
Drain the lentils, discarding the herb pouch, carrot, and onion. Transfer to a large bowl and add 1 tsp. salt and the remaining 1 Tbs. vinegar, tossing to coat.
Drain the sausage, and, if necessary, peel off the casing (bite into a piece first—many sausage casings are thin enough to leave on). Slice into 1/4-inch rounds. Add the sausage and vinaigrette to the lentils, tossing to coat. Stir in the parsley and scallions, and season with a generous amount of black pepper, plus more salt and vinegar to taste.
nutrition information (per serving):
Size : based on six servings; Calories (kcal): 390; Fat (g): 21; Fat Calories (kcal): 180; Saturated Fat (g): 3.5; Protein (g): 17; Monounsaturated Fat (g): 9; Carbohydrates (g): 30; Polyunsaturated Fat (g): 6; Sodium (mg): 610; Cholesterol (mg): 25; Fiber (g): 7.