How to Make It
Put the potatoes in a medium saucepan of salted water. Bring to a boil and cook until the potatoes are just tender, about 5 minutes. Drain the potatoes and put them in a glass or stainless-steel bowl. Add the chicken broth and 1/4 teaspoon of the salt to the warm potatoes and toss gently.
Meanwhile, in a large glass or stainless-steel bowl, whisk together the mustard, vinegar, the remaining 1/4 teaspoon salt, and the pepper. Add the oil slowly, whisking.
Put a large nonstick frying pan over moderate heat. Add the smoked sausage and cook, stirring occasionally, until the sausage is brown and warmed through, about 3 minutes. Remove the sausage and drain on paper towels.
Toss the potatoes with 2 tablespoons of the dressing and the parsley. Toss the romaine into the remaining dressing. Put the lettuce on plates and top with the potatoes and sausage.