Shrimp Salad with Potatoes and Green Beans
1 lemon wedge plus 2 Tbs. fresh lemon juice 4 green onions, white and light green portions finely chopped, trimmings reserved 3 Tbs. minced fresh dill, stems reserved 3/4 lb. boiling potatoes cut into 1-inch pieces 3/4 lb. green beans cut into 1 1/2-inch pieces 1 tsp. whole-grain Dijon mustard 3 Tbs. extra-virgin olive oil …