Heat a large skillet and add enough olive oil to saute your veggies.
Add 1/2 of a red onion and 1 orange bell pepper, both roughly chopped.
Once the veggies are soft, add 6 cups of mustard greens, cleaned and chopped.
Add 2 cloves of minced garlic and 1 cup of low sodium veggie stock, stir and let simmer for about 10 minutes.
Add 2 tablespoons of dusseldorf mustard and a bit or a lot of butter, to finish off your sauce. Turn the heat down to low and let the greens relax for a few minutes before turning off the heat and serving them.