3 tablespoons extra-virgin olive oil, plus more for serving
1 pound sliced mixed mushrooms
Kosher salt and freshly ground pepper
1 tablespoon unsalted butter
3 garlic cloves, smashed
2 teaspoons herbes de Provence
1 tablespoon sherry vinegar
1 tablespoon soy sauce
2 teaspoons chopped fresh oregano
In a large skillet, heat oil over medium-high. Add mushrooms and cook, undisturbed, until bottoms are golden brown, 3 minutes. Season with kosher salt and freshly ground pepper. Cook, stirring, until mushrooms are golden all over, about 5 minutes more (if browning too quickly, reduce heat).
Add butter, garlic, herbes de Provence, sherry vinegar, and soy sauce; cook 30 seconds. Transfer to a bowl and stir in oregano; drizzle with more oil. Let stand at least 1 hour, or refrigerate, covered, up to 2 days. Serve at room temperature.