In a 12-inch skillet or braiser over medium heat, melt the butter.
Add in the onions, salt and pepper. Cook just until transparent.
Add in the flour and cook for about a minute until the roux starts to turn golden.
Slowly pour in the milk and chicken broth. Cook until just thickened and take off the heat.
Add the chicken bouillon and poultry seasoning and stir until combined. Add in the defrosted green beans and stir to combine.
Place in the preheated oven and bake for 30-40 minutes or until it starts to bubble up the sides.
While the green beans are baking, toss the shallots in the cornstarch, onion powder, and white pepper. Pour canola oil in a saucepan up to about an inch. Place over medium/high heat.
Once up to temperature (350 degrees or once a small bit of the shallots bubble when dropped in) place the shallots in and cook until golden brown. Remove from the oil and place onto a paper towel. Immediately sprinkle with fine table salt.
Once the green beans are finished baking, sprinkle on the crispy shallots.