Start by blanching the green beans. Prepare an ice bath - fill a large bowl with ice and cold water.
Bring a large pot of water to a boil. Once boiling, add the green beans and cook for 3 to 4 minutes. Use a strainer to immediately transfer the beans to the ice bath. Let them chill in the bath for 5 minutes. Pat the beans dry with a paper towel.
Place the beans on the plate and give them a light sprinkle of salt and pepper. Drizzle on the dijon dressing. Top with the crumbled blue cheese and walnuts. Serve immediately. This is incredible cold - like leftovers right out of the fridge.
In a bowl, whisk together the lemon juice and mustard. Whisk in the oil until the dressing is emulsified. Add a pinch of salt and pepper along with the herbs. Whisk to combine. Any extras of this stays great in the fridge for a few days - it just has to be whisked and stirred before using!