Heat 2 tablespoons of olive oil in a large saucepan, add the leeks, and cook uncovered over medium heat for 5 minutes. Add the carrots and cook for one minute. Add the lentils, onion, turnip, and 6 cups of water. Bring to a boil, lower the heat, and simmer uncovered for 20 to 25 minutes, until the lentils are tender. Discard the onion and turnip and drain the lentils, reserving some of the cooking liquid. Place the lentils in a large bowl
Meanwhile, in a small bowl or glass measuring cup, whisk together the garlic, mustard, vinegar, 2 teaspoons salt, and 1 teaspoon pepper. Slowly whisk in 1/2 cup olive oil, add to the lentils, and toss. If it's dry, add a few tablespoons of the reserved cooking liquid.
Add the scallions, thyme, parsley, kielbasa, 2 teaspoons salt, and 1 teaspoon pepper and toss. Set aside to cool.
Toast the baguette slices and spread with the goat cheese. Taste the salad for seasonings and serve at room temperature with the goat cheese toasts.