Rinse the lentils in cold water and add to a small pot. Cover with 4 cups of water, add a tablespoon of salt, and bring to a boil over medium-high heat. Reduce the heat to medium-low, cover, and cook for 25-30 minutes, until the lentils are tender but still have a slight bite. Drain the lentils and rinse with cold water to stop the cooking. 

Prepare the vinaigrette: In a small bowl whisk together the oil, vinegar, mustard, honey, shallot, salt and pepper to taste, and 1 tablespoon of water. Taste and adjust seasonings. 

In a large bowl mix together the lentils, vinaigrette, and scallions. Toss lightly to combine and serve.