In a small bowl, combine the sliced steak and the mustard. Coat the steak and set aside.
Steam the green beans and broccoli until tender. Set aside.
In a non-stick skillet, add the olive oil, garlic, leaks, carrots, celery, and chili pepper (don’t forget to remove the seeds!). Saute until tender. Turn off heat.
Transfer the green beans and the broccoli to the skillet with the rest of the vegetables. Stir to combine.
In a medium pot, add the water, bullion cube, and thyme and bring to a boil. Reduce to low heat.
Transfer all of the vegetables and the marinated steak to the stock. Stir to combine.
Allow to simmer for a few minute so the flavors combine. Add salt and pepper to taste.