In a large sauté pan set over medium heat, melt the butter until foaming. Add the chopped shallots and cook, stirring until softened, about 3 minutes.
Sprinkle the flour and the seasoning mix into the pan and stir to coat shallots. Slowly whisk in the chicken stock, whisking out any lumps; then the half and half.
Simmer for 2 minutes or just until thickened; then stir in cheese and remove from heat. Combine green beans and onion sauce and pour into a 9x9 casserole dish.
Bake for 20 to 25 minutes until liquid has reduced and thickened. Remove from oven and top with crisp onions.