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This grilled cheese recipe from the ‘Umami Bomb’ cookbook is one of the best we’ve tried in while and it’s peak comfort food. A great grilled cheese sandwich depends on several factors, but this genius umami-boosting secret ingredient is one grilled cheese trick you’ve never tried before.

Umami has come a long way since 1908 when a Japanese chemist first isolated the savory flavor. For the better part of a century, folks debated whether it was indeed an official taste (along with sour, sweet, bitter, and salty) and though it’s been properly designated it’s still not as easily identified as the others.

Even if it’s not always at the forefront of our consciousness, umami is still truly beloved. Food rich in umami like miso, tomato sauce, soy, fish sauce, mushrooms, and nutty hard cheeses are very often the star flavor in some of our most crave-able foods. There’s no denying what ketchup means to a plate of fries or parmesan to a bowl of pasta, and we all have glorious umami to thank for that.

That’s much of what Raquel Pelzel was thinking when she wrote her latest cookbook, “Umami Bomb,” which delivers 75 (mostly) vegetarian recipes all bursting with umami like a simple soy marinara, and falafel-spiced grilled mushrooms. Though not a full vegetarian herself Pelzel hopes to promote more vegetable-eating for the health of ourselves (and the planet) and purports that adding more umami is a good way to make that proposition appealing.

Umami often shows up when glutamates are released during the cooking of certain foods like onions, for instance. Caramelized onions are one of the fastest ways to impart good umami into just about anything. This grilled cheese gets a second helping of umami from miso butter earning a rating of two (out of three) “Umami Bombs” from Pelzel in her book.

Pelzel says “avoid getting too excited and adding the miso butter to the outside of the bread—the miso will burn up before the bread gets toasty and golden.” This would also work great with Onion and Rosemary Jam (also from “Umami Bomb”) for a little sweetness.

  • 4 tablespoons (1/2 stick) unsalted butter at room temperature
  • 1 tablespoon extra-virgin olive oil
  • 1 large yellow onion, peeled, halved, and thinly sliced
  • 1/2 teaspoon kosher salt
  • 1 tablespoon rice vinegar
  • 1 heaping tablespoon miso paste (I like white miso, but a darker miso works, too)
  • 1 tablespoon whole-grain mustard
  • 4 slices good-quality sandwich bread
  • 1 cup grated gruyère cheese (or 1/2 cup grated gruyère with 1/2 cup grated gouda for extra umami)
  • Cornichon pickles, for serving (optional)

  1. Melt 1 tablespoon of butter in a large nonstick skillet set over medium-high heat.
  2. Add the oil, onion, and salt and cook, stirring often, until the onion is soft and browned in spots, 8 to 10 minutes.
  3. Stir in the vinegar and turn off the heat.
  4. Transfer the onion to a small bowl and set aside (don’t wash the pan).
  5. Mix 1 tablespoon of the remaining butter with the miso paste and mustard in a small bowl.
  6. Spread one side of each bread slice with the remaining 2 tablespoons of butter. Spread the other side with the miso butter. Place two of the bread slices, plain buttered side down, in the pan.
  7. Divide the cheese and onion evenly between them and top with the other bread slices, plain buttered side up.
  8. Cook over medium-low heat until the bread is golden brown, 4 to 5 minutes (do not press the sandwich down with a spatula—just let it be).
  9. Flip the sandwiches over and cook on the other side until the bread is golden brown and the cheese is melted, 3 to 4 minutes longer.
  10. Transfer to plates and serve immediately with pickles. Lots of pickles.