Makes 5 or 6 servings
A golden path to popularity, this is a great use for leftover flat beer. It can also be made with present-tense, still-perky beer—in the unlikely event that “leftover” means the other half of the one you’re drinking while you read this.
Different beers can yield vastly different flavors, and it’s fun to experiment with various light and dark varieties when making beer-cheese sauces, such as this one (which is a riff on Welsh rarebit). Continuing the theme, plan to drink something that matches (chilled bottles from the same sixpack, perhaps?) with your dinner.
In a pinch, you can use a 10-ounce package of frozen chopped spinach instead of the fresh. Defrost thoroughly and squeeze as dry as possible ahead of time.
Nonstick cooking spray
1/2 pound orecchiette, elbow macaroni, or equivalent-sized shells
1 tablespoon olive oil, plus a little more for the pasta
1 cup milk (low-fat is OK)
1 tablespoon unsalted butter
1/2 pound mushrooms, wiped clean, stemmed as necessary, and cut into 1/2-inch dice
1 teaspoon salt, or more to taste
1 teaspoon minced or crushed garlic
1 teaspoon prepared Dijon or plain yellow mustard
2 tablespoons unbleached all-purpose flour
1 cup room-temperature beer (your choice)
1 pound fresh spinach, stemmed as necessary and chopped (4 packed cups)
1 1/2 (packed) cups grated sharp white cheddar (6 ounces)
3/4 cup fresh whole-wheat bread crumbs
1/2 cup minced walnuts (optional)
1. Preheat the oven to 350°F, with a rack in the highest position that will fit your baking pan. Lightly spray a 2-quart baking dish or an 8-inch square pan with nonstick spray.
2. Put on a medium-large pot of water to boil. When the water boils, add the pasta and cook until just tender enough to bite into comfortably, then drain and transfer to a bowl. Toss with a little olive oil and set aside.
3. Heat the milk—ideally in a spouted measuring cup in a microwave—until it is steaming and too hot to touch, but not boiling. Set the hot milk near the stove.
4. Place a medium-large saucepan over medium heat for about a minute, then add the oil and swirl to coat the pan. Toss in the butter, letting it melt into the oil. Add the mushrooms and ½ teaspoon of the salt and cook, stirring, over medium-low heat for 5 minutes.
5. Whisk in the garlic and mustard, then turn the heat to low and sprinkle in the flour, whisking constantly; it will quickly become a paste. Continue to whisk for another 15 seconds or so.
6. Keep the pan over low heat as you drizzle in the hot milk, whisking constantly. When the milk is incorporated, whisk in the beer. Turn up the heat to medium and stir constantly with a wooden spoon as you add the chopped spinach and the remaining ½ teaspoon salt. Cook for about 5 minutes, or until the spinach wilts its way into the sauce. Remove the pan from the heat and stir in both the cooked pasta and the cheese.
7. Taste for salt, add a touch more if you wish, then transfer the mixture to the baking pan. Top with the bread crumbs and walnuts, if desired, and bake uncovered for 15 to 20 minutes, or until bubbly around the edges and crisp and golden on top. (It might look loose on its way into the oven, but it will pull itself together by the time it comes out.) Serve hot.