Clean the beans by rinsing them, and removing both ends.
Pat them dry and transfer to a mixing bowl.
Pre-heat the oven to 350 F.
Cut the onion in wedges.
Dress the beans with olive oil, salt, pepper, sugar, herbs and Dijon. Stir and make sure all the beans are nicely coated with the dressing. Add the onion wedges, and give it one more stir.
Transfer to a baking sheet and bake at 350 F for 1 hour, stirring and mixing them every 10 minutes or so. If they are still too crunchy for you after 1 hour, keep cooking for an extra 30 minutes.
These beans will keep a lovely crunch and the onions a beautiful caramelization. Serve warm and enjoy as a side, or as the main dish with a soft boiled egg.