I adapted this from Alton Brown and from Smitten Kitchen, to whom I am eternally grateful, because this is maybe the best serves-two vegetable dish in all creation. Really, it’s That Good. We’ll be making this again soon.
There are really three recipes in this post: one for the onions (I want to try them as a component in a sandwich!), one for the creamy mushroom sauce, and then, finally, the recipe for the casserole itself.
Crispy Onions (make lots, because they’ll be snitched all afternoon)
- 1 medium yellow onion, halved and sliced thinly
- 2 Tbsp flour
- 1 Tbsp fresh breadcrumbs
- 1/4 tsp salt
- freshly ground pepper
- canola or peanut oil, for deep frying
Toss the onions with the flour and seasonings. The idea is to coat every little onion string with some goodness. Heat 1/2″ of oil in a 10-inch skillet until a drop of water flicked into it will hiss and sputter. Add the onions – just a few at a time – so they make a single layer. Fry until they are a light golden brown, then remove to a paper-towel covered sheet pan or plate. Repeat with remaining onions. Set aside, uncovered, until needed. Be prepared to defend them against snackers.
- 1 Tbsp unsalted butter
- 4 oz mushrooms, coarsely chopped
- a pinch nutmeg
- freshly ground black pepper
- 1/4 tsp salt
- 1 small garlic clove, minced
- 1 Tbsp flour
- 1/2 c chicken or vegetable broth
- 1 1/2 Tbsp heavy cream
Over medium-high heat, melt the butter in the bottom of a 10″ skillet. Add mushrooms, salt, and pepper; sauté them until they start releasing their liquid, anywhere from 3 to 5 minutes. Add the garlic, sauté briefly, just until it releases its fragrance, then add the flour, and stir it until it coats the mushrooms. Add the broth a bit at a time, stirring, and simmer it for a minute or two. Add the cream, and bring back to a simmer, cooking until the sauce thickens a bit, about 5 minutes, stirring frequently.
Prep the beans
- 1/2 lb green beans, trimmed and cut
Bring a large saucepan of salted water to a boil, and cook the beans for about 5 minutes, until crisp-tender. Drain, then shock them in cold water to stop the cooking, and drain again. Set aside until needed.
Finally! Assemble the Casserole
Add the cooked green beans to the mushroom sauce, and stir until they are coated. You can bake the casserole directly in the skillet, if it has an oven-proof handle, or you can turn the beans and sauce into a lightly greased shallow baking dish. Top with the crispy onions. Bake at 400˚ for 15 minutes or so, until the sauce is bubbling and the onions are just a shade darker.
Notes on cooking ahead: the onions can be made up to a full day in advance. Hold them at room temperature, loosely wrapped (not airtight, or else they’ll get soggy.) The green beans can be cooked ahead and kept in the refrigerator until needed, as can the mushroom sauce. For that matter, the beans may be combined with the sauce and kept in the refrigerator for a day. Just top with the onions and bake right before serving, and you’ll be fine.