Heat the olive oil in the cast-iron skillet and cook the onions on medium heat for 3-4 minutes.
Add the mushrooms and to the onions and continue to cook for 4-5 minutes,
Add the flour and and using a whisk mix it through.
Once combined, add the chicken stock and simmer for 2 minutes on med-low heat. Then add in the half and half, Cook until the sauce thickens, then add in the string beans. Next, you will broil the crispy onions