Soy Sauce Glazed Butter Mushroom Sandwich Recipe

French Butter: The key to achieving that luxurious, melt-in-your-mouth quality is using French butter. Known for its higher fat content and creamy texture, it adds a rich, buttery flavor that’s hard to replicate with regular butter. It’s perfect for both caramelizing the onions and browning the mushrooms, bringing out their natural flavors.

Shiitake Mushrooms: These mushrooms are packed with umami, the savory taste that makes dishes so satisfying. Shiitakes have a meaty texture that holds up well during sautéing, and their earthy flavor pairs beautifully with the soy sauce and butter in this recipe. If you can’t find shiitakes, cremini or portobello mushrooms are great substitutes. Both have a similar texture and will soak up the flavors just as well.

Parmigiano Reggiano Cheese: This hard Italian cheese brings a nutty, salty flavor that complements the buttery mushrooms and onions. Shaving it into the arugula salad adds a touch of elegance and a burst of umami that ties the whole sandwich together. If Parmigiano Reggiano isn’t available, you can use Grana Padano or Pecorino Romano as substitutes. Grana Padano is slightly milder but still offers a rich flavor, while Pecorino Romano has a sharper taste that adds an extra kick.

Caramelizing the Onions: To achieve deeply caramelized onions, cook them low and slow over medium-low heat, stirring every few minutes. This method allows the natural sugars in the onions to develop a rich, sweet flavor. Be patient—this process can take up to 40 minutes, but the result is worth it. Adding the soy sauce at the end enhances the umami and balances the sweetness of the onions.

Sautéing the Mushrooms: When sautéing the shiitake mushrooms, make sure your skillet is hot enough to sear them quickly. This ensures they become golden brown and slightly crispy on the edges without becoming soggy. Deglazing the pan with soy sauce not only adds flavor but also helps lift all the delicious bits stuck to the pan, making the mushrooms even more flavorful.

Toasting the Bread: For perfectly toasted sourdough, use a generous amount of butter in the pan and drag the bread through it to soak up the buttery goodness. Toasting both sides gives the bread a golden crust while keeping the inside tender. Don’t skip the pinch of salt after flipping—it enhances the overall flavor of the sandwich.

Dressing the Greens: When preparing the arugula salad, toss it gently to avoid bruising the leaves. The lemon juice and shaved Parmigiano Reggiano add a refreshing acidity and umami, balancing the richness of the mushrooms and onions. Chill the salad in the refrigerator until you’re ready to assemble the sandwich to keep it crisp.