Oats thicken the casserole.
Drain the artichoke hearts in a colander, quarter the artichoke hearts and squeeze dry with paper towels; set aside. In a large pot of boiling salted water, cook green beans until tender, 4 to 6 minutes. Drain and set aside. Preheat oven to 425°F. In a large saucepan, heat olive oil over medium heat. Whisk in almond meal and garlic and cook, whisking, for 1 minute (do not let brown). Gradually whisk in milk; bring to a boil. Reduce to a simmer and cook until sauce has thickened, 2 to 3 minutes. Stir in green beans, chicken and artichoke hearts. Season with salt, pepper, and a sprinkle of cayenne. Transfer to a shallow 2-quart baking dish. Spread the oats on a dinner plate and give them a quick spray with cooking spray. Scatter them over the artichoke/bean mixture. Push the oats into the mixture so they get moistened with milk. Bake until the sauce is bubbling, 10-12 minutes. Serve with 1/3 cup mandarin orange sections each for dessert.