Put vinegar, garlic powder, shallots, mustard and herbs together in a bottle or medium bowl, whisk in enough oil to emulsify dressing. Season to taste with salt and pepper. Set aside.
Toss all salad ingredients together in a large bowl. Add a little dressing and toss again, taste and add more dressing as necessary.
*Blanch and cool green beans: Bring a large pot of water to a boil. Meanwhile prepare an ice water bath, a large bowl filled with ice and water.
When the water boils add the green beans and a good amount of salt, boil for 3 minutes then plunge them into the ice water bath.