1. Add the potatoes to a stock pot and cover with water to an inch above the level of potatoes. Add 1 ½ teaspoons salt, cover, and place on the stove top over high heat. Bring to a boil. Once boiling, remove the lid and cook for 5 minutes. Add the green beans and boil for another 5 minutes. When done, potatoes should pierce easily with a fork. Check frequently. Drain and spread potatoes and green beans on a baking sheet to cool for approximately 10-15 minutes. You can speed up cooling by placing them in the refrigerator if you have the space.
2. While the potatoes and green beans cook, make the vinaigrette. In a small bowl whisk together the mustard, vinegar, olive oil, thyme, and ½ teaspoon salt. Taste and adjust salt if needed.
3. In a large bowl toss the red pepper, onion, olives, parsley, and tomatoes with the vinaigrette. Once the potatoes and green beans have cooled to room temperature, add to the bowl and gently toss. Season with salt and pepper to taste and refrigerate for at least 30 minutes before serving. Serve as is or with optional toppings.