Trim mushroom stems and wipe caps with a damp towel. Slice larger mushrooms about 1/4 inch thick; leave small mushrooms halved or whole so pieces are uniformly sized.

Heat a large heavy skillet (cast-iron or stainless) over medium-high heat until hot, about 2 minutes.

Add olive oil and 1 tablespoon of butter to the pan. Swirl to coat and allow butter to melt and begin to foam but not brown.

Add the mushrooms in a single layer. Do not crowd the pan; if necessary, cook in two batches. Let mushrooms sear undisturbed for 2–3 minutes so they develop color.

Stir or toss mushrooms and continue cooking, stirring every 1–2 minutes, until they release their liquid and it evaporates and mushrooms are deeply browned, about 6–8 more minutes total.

Push mushrooms to the side of the pan and add the remaining 1 tablespoon butter. Add the diced shallot and cook, stirring, until softened and translucent, about 1–2 minutes. Add minced garlic and cook 30–45 seconds until fragrant (do not burn).

If using, deglaze the pan with the white wine or vermouth: pour it in, scraping up browned bits with a wooden spoon, and simmer 1 minute to reduce slightly.

Herbs & finishing

Stir the shallot/garlic mixture together with the mushrooms so everything is evenly combined.

Add fresh thyme leaves, chopped parsley (reserve a little for garnish), lemon juice, salt, and pepper. Toss to coat and cook 30–60 seconds to marry flavors.

Taste and adjust seasoning, adding a pinch more salt or a squeeze more lemon if needed.

Transfer the poêlée to a warm serving dish. Garnish with chopped chives if using and the reserved parsley. Serve immediately.