We were prepping our sirloin steak with garlic-herb butter and I found this recipe while looking for a flavorful side dish. Buttery, herby with a touch of tang thanks to tamari and balsamic, you'll love these mushrooms and find that you can pair them with anything - especially grilled steak.
1 large or 2 small shallots, peeled and finely diced
3 tablespoons unsalted butter, divided
1 pound portobello mushrooms, sliced 1/8-inch thick
1/2 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
1 1/2 teaspoons finely chopped fresh rosemary or thyme leaves
2 tablespoons balsamic vinegar
1 tablespoon packed light brown sugar
1 tablespoon tamari or soy sauce
3 cloves garlic, finely minced or grated
Heat one tablespoon butter in a large frying pan or cast iron skillet over high heat until shimmering, about 15 to 20 seconds. Add the shallots and cook until they begin to soften and brown at the edges, 1 1/2 to 2 1/2 minutes.
Add remaining 2 tablespoons of butter and stir until melted. Add the mushrooms, salt, pepper, and rosemary or thyme and stir well. Cook, stirring frequently to prevent burning, until the mushrooms have a rich brown color on the edges and some of the sides, and have just begin to release their juices, 3 to 4 minutes.
Reduce the heat to medium-low, add the vinegar, sugar, tamari, and garlic. Cook, stirring occasionally, until the mushrooms are soft and tender and the liquid reduces in volume considerably, thickens to the consistency of agave or maple syrup, and coats the mushrooms, 6 to 8 minutes.
Recipe adapted from Tami Weiser, contributor to The Kitchn