This is really just potatoes and green beans roasted together and then covered with cheese, but casserole is not a very appealing term for something so delicious.
Heat the oven to 400 degrees.
Trim 1/2 lb. of Green Beans and spread on a cookie sheet. Toss with 1/2 T. olive oil and salt to taste, then arrange in a single layer.
Wash 2 lbs. of potatoes and then cut into “green bean” sized julienne strips, also known as “Fries”. Spread on a 2nd cookie sheet, drizzle with 1 T. olive oil and salt to taste.
Place both cookie sheets in the oven. Peel and mince 3 cloves of garlic. Grate gruyere, cheddar or monterey jack cheese to make 1 1/2 C.
Roast the vegetables until they are sizzling and begin to brown, then stir to turn them and continue to cook until the potatoes are nicely browned and the green beans are tender — about ten minutes longer.
Remove both pans from the oven. Sprinkle the garlic over the potatoes, then transfer the green beans onto the potato pan too. Stir to combine. Sprinkle with black pepper, then distribute the grated cheese over the entire pan as evenly as possible.
Return the pan to the oven and roast for another 5-10 minutes, until the cheese is completely melted and beginning to get crispy.
Serve with a side of Arugula salad.