Wash potatoes and slice in quarters. Place potatoes in medium sauce pot and cover with water. Bring water to boil on high and cook potatoes 4-5 minutes.
Add green beans to pot and continue cooking 4-5 more minutes until potatoes are fork-tender. Remove sauce pot from heat and drain vegetables; reverse.
Pat pork chops dry with a paper towel, then season with 1/4 teaspoon each salt and pepper. Place bread crumbs in shallow bowl; coat pork with mustard. Dredge pork in bread crumbs and press lightly to coat.
Add onions, potatoes, and green beans to the same pan and cook 4-5 minutes, stirring occasionally, until onions are softened and potatoes brown slightly. Add one-half of vinaigrette and 1/4 teaspoon of each salt and pepper to pan; toss to coat. Serve vegetables with pork chops and drizzle with remaining vinaigrette.