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Grilled cheese is elemental. All you need is the right cheese (I like Gruyere or sharp cheddar), the right bread (I go for a soft sandwich bread), a little butter and a pan, and you’re on the way to a quick, simple, satisfying meal. Or at least the main thrust of one, rounded out by good old tomato soup and/or a salad.

But you don’t need a recipe for a plain grilled cheese sandwich, do you? What you need is a recipe that takes grilled cheese to the next level with just a couple of smart additions, like the ones Raquel Pelzel offers in her terrific new book, “Umami Bomb.” She focuses on ingredients that can add umami, the delectable fifth taste that’s sometimes called savory. But not just a touch of umami. As you can tell by the title, this is about a real punch of flavor, about vegetarian recipes that, as she says in the subtitle, “explode with flavor.”

The umami-rich ingredients include aged cheeses, soy sauce, tomatoes, mushrooms, smoke, nutritional yeast and, in the case of these sandwiches, caramelized onions and miso.

I’m an avowed fan of all of the above, with such an affection for the last two on the list that I had little doubt about which recipe I’d pick from Pelzel’s book. And I wasn’t disappointed. It takes a bit of time to properly caramelize onions, of course, but after that, the recipe goes almost as quickly as a conventional grilled cheese: You just mix up the miso with butter and whole-grain mustard and slather that on the inside of the sandwiches, with plain butter on the outside for pan-frying. The result is as indulgent as you’d expect when eating grilled cheese for dinner (this is not health food by any means), but with a welcome tang and, of course, the “pow!” of umami in every bite.