Wipe mushrooms with a damp paper towel to remove dirt. Trim stems as needed and slice larger mushrooms into 1/4-inch (6 mm) slices; leave small mushrooms halved or whole so pieces are uniform in size.

Heat pan

Place a large heavy skillet (preferably stainless steel or cast iron) over medium-high heat. Add the olive oil and 1 tablespoon of the butter and let the fat get shimmering but not smoking (about 1 minute).

Sear mushrooms

Add the mushrooms in a single layer — do not overcrowd the pan. Allow them to sear undisturbed for 2–3 minutes so they develop color, then stir or toss and continue cooking another 2–3 minutes until most of the moisture has evaporated and edges are golden-brown.

Add aromatics

Push mushrooms to the side, add the remaining tablespoon of butter to the cleared area, then add the minced shallot and cook 1–2 minutes until translucent. Add the garlic and thyme and cook 30–45 seconds until fragrant, stirring with the mushrooms so the aromas combine.

Liquids & Finishing

Deglaze

Pour in the white wine and use a wooden spoon to scrape up any brown bits from the bottom of the pan. Let the wine reduce until mostly evaporated, about 1–2 minutes.

Simmer with stock

Add the stock and stir. Bring to a gentle simmer and cook 1–2 minutes to concentrate flavor and to finish cooking the mushrooms. If using cream, reduce heat to medium-low and stir in the cream now, simmering gently 1–2 minutes until sauce is slightly thickened.

Season & finish

Stir in the lemon juice, chopped parsley, salt, and black pepper. Taste and adjust seasoning — add more salt or lemon if needed. If using cheese, sprinkle grated Parmesan and stir until melted and incorporated.

Serve

Spoon the mushrooms into a warm serving dish. Garnish with extra parsley and a light drizzle of olive oil if desired. Serve immediately on toasted bread, crostini, or alongside grilled meat, pasta, or polenta.