I was all set to make a grown up version of green bean casserole using no canned soup or container fried onions. Then I went to chop my baby bella mushrooms and the babies had grown beards. Not good (sign, groan, roll eyes and sidestep to plan b).
The casserole now morphs into Green Bean Gratin with a very French caramelized shallot cream sauce and golden crust of skinny onion crisps and grated Parmesan. What started out as a major annoyance ended up pleasing me so much. Lemons to lemonade.
I don't think I will never go back. This is recipe too good. —HeidiMoyer
Preheat oven to 425*, grease a baking sheet with cooking spray.
Make onion crisps: Combine sliced white onion, flour, salt and panko in a bowl, toss to coat. Tumble onto baking sheet and bake for 20-30 minutes, turning the onions every 5 minutes to keep from burning. Remove and set aside. Turn oven down to 375*.
In a deep, 10-inch cast iron or non-stick skillet, melt the butter over medium-high heat. Add the shallot, salt, pepper and sugar, and cook for 5 minutes or until translucent. Turn heat to low and continue cooking and stirring until shallot is soft, dark brown, and caramelized-about 20 minutes.
Make cream sauce: Sprinkle flour over shallots and stir to combine well, cook for 5 minutes. Add milk, broth, and nutmeg. Turn heat up to medium and allow to slow-simmer until sauce is thickened, about 5 minutes. Remove from heat.
Tip the green beans into the skillet and mix with the sauce. If skillet is cast iron or oven-proof, sprinkle over onion crisps and Parmesan cheese. Alternatively, spoon the mixture into a baking dish before topping with onions and cheese. Cover with foil and bake for 30 minutes. Remove foil and bake 5-10 minutes longer until browned and bubbly. Sprinkle with dried parsley before serving (optional).