Classic Green Bean Casserole | Heinen's Grocery Store

Ingredients

• 1 lb. white onions, halved and thinly sliced
• 2 cups buttermilk
• 2 cups flour
• 1 tsp. salt
• 4 cups vegetable oil
• Flaky salt, for topping
• 2 Tbsp. Heinen’s unsalted butter
• 8 oz. cremini mushrooms, sliced
• 1 shallot, thinly sliced
• 4 Tbsp. Heinen’s unsalted butter
• 1/3 cup flour
• 3 cups Heinen’s whole milk
• 1 cup Heinen’s Parmigiano Reggiano, shredded
• 1/2 tsp. salt
• 1/4 tsp. black pepper
• 1 package Heinen’s frozen French cut green beans, cooked and drained
• 8 oz. can sliced water chestnuts, drained