Preheat oven to 375 degrees.
Toss shallots in all-purpose flour. Shake off. Pour vegetable oil to about 1 inch high in a medium saucepan. Heat oil. Fry shallots, in batches, 3 to 4 minutes or until crispy and just golden. Drain on paper towels.
Bring a large pot of salted water to a boil.
Add in the green beans and cook for 5 minutes.
Remove from the boiling water and immediately put them into ice water to stop the cooking.
Drain the green beans and set aside.
In a large skillet melt the butter and add the olive oil over medium heat.
When the skillet is hot add in the mushrooms and onions. Saute for 6-8 minutes.
Sprinkle the flour over the mixture and stir until you can no longer see the flour.
Slowly pour in the chicken broth stirring the entire time until the sauce starts to thicken, about 1 minute.
Lower the heat to medium-low and add in the sherry, Worcestershire sauce, cream and milk.
Cook for about 3 minutes, stirring occasionally.
Stir in the green beans.
Spray a 13 x 9 baking dish with cooking spray. Then add the green bean mixture. Top with fried shallots.
Bake for 25 minutes. If the topping starts to get too brown cover loosely with foil.