Homemade Fried Onions

1. Thinly slice the two large yellow onions and place them in a bowl. Cover with buttermilk and soak for 10–15 minutes.
2. While the onions soak, combine the flour, coarse kosher salt, black pepper, and garlic powder in a bowl.
3. Preheat approximately 2 inches of oil in a heavy skillet to 350°F. Line a baking sheet with a couple of layers of paper towels.
4. Remove batches of onions from the buttermilk and shake off the excess. Toss them in the seasoned flour mixture.
5. Fry the onions in small batches for 1–2 minutes, until golden brown.
6. Use a metal strainer to transfer the onions to the paper towel-lined baking sheet. Spread them out to cool uncovered so they stay crispy.

Blanch the Green Beans

1. Trim the ends of the green beans where they were attached to the vine. Cut them in half or leave them whole.
2. Prepare a large bowl of ice water by combining cold water with a couple of cups of ice.
3. Bring a large pot of water to a boil. Add the green beans and boil for 2–4 minutes, depending on their thickness.
4. Immediately transfer the green beans from the boiling water into the ice water.
5. Once cooled, remove the green beans and pat them dry with paper towels.

Creamy Mushroom Sauce

1. Preheat a large cooking pan over medium heat.
2. Thinly slice the small yellow onion and baby bella mushrooms.
3. Add the canola oil and sliced onion to the pan. Sauté until the onion becomes transparent.
4. Add the mushrooms and cook until mostly done.
5. Mince or press the garlic and add it to the pan. Cook until fragrant.
6. Sprinkle the flour over the vegetables and stir until they are coated.
7. Slowly pour in the milk while whisking continuously. Add the heavy whipping cream while continuing to stir.
8. Stir slowly as the mixture thickens. Season with salt and black pepper, then cook for a couple of minutes.
9. Remove the sauce from the heat.

Assemble the Casserole

1. Preheat the oven to 375°F and lightly grease a 9×13-inch casserole dish.
2. Add the green beans to the casserole dish. Pour in the mushroom cream sauce and add 1/2 cup of the fried onions.
3. Mix until everything is evenly combined.
4. Cover with foil and bake for 35–45 minutes, depending on whether you prefer crunchier or softer green beans.
5. Carefully remove the foil and spread the remaining fried onions over the top.
6. Bake uncovered for another 7–10 minutes.