Gently pat the 10 ounces fresh oyster mushrooms dry with a clean towel. Trim off the hard stem at the base of each mushroom clump and separate large clusters into bite-sized pieces.
Heat a large nonstick pan over medium-high heat. Add 1 tablespoon extra-virgin olive oil and heat until shimmering.
Add enough mushrooms to form a single layer (work in batches if needed so they don't crowd). Cook without moving until the underside is golden brown and crisp, about 3–5 minutes. Season with salt and freshly ground black pepper to taste, then toss or flip and continue cooking briefly so other sides brown. Transfer the cooked mushrooms to a plate and repeat with any remaining mushrooms.
Reduce the heat to low. Add 2 tablespoons unsalted butter to the same pan. When the butter begins to melt, add 2 cloves garlic (finely chopped), 2 tablespoons fresh parsley (chopped), and the chopped leaves from 2 sprigs fresh thyme.
Stir the butter, garlic, and herbs over low heat until the butter is fully melted and the garlic is fragrant, about 30–60 seconds—avoid letting the garlic brown.
Pour the herbed garlic butter over the cooked mushrooms, toss to coat, taste and adjust salt and pepper if needed, and serve immediately.