Place each cutlet between two sheets of plastic wrap and gently pound with a meat mallet to about 1/4-inch (6 mm) thickness. Season both sides with salt and pepper.

Put flour in one shallow dish, beaten eggs in a second, and breadcrumbs in a third.

Dredge each cutlet in flour (shake off excess), dip in egg, then coat evenly with breadcrumbs. Press gently so crumbs adhere.

Heat 2 tablespoons oil in a large skillet over medium-high heat. Add cutlets (work in batches if needed) and fry until golden brown, about 3–4 minutes per side.

Transfer to a baking sheet and keep warm in a low oven (200°F / 95°C) while you make the sauce. Tip: Add a little more oil between batches if the pan looks dry.

In the same skillet, lower heat to medium and add remaining oil + butter (if using). Sauté the chopped onion for 3–4 minutes until translucent, then add mushrooms and cook another 4–5 minutes until they release liquid and begin to brown.

Add garlic and cook for 30 seconds until fragrant.

Stir in tomato paste (if using), then pour in the broth and scrape any browned bits from the pan. Simmer gently for 5–7 minutes until the sauce reduces slightly.

Stir in cream and Dijon mustard (if using). Simmer 1–2 minutes until warmed through and slightly thickened. Taste and season with salt and pepper.

Nestle the breaded cutlets into the sauce for 1–2 minutes to rewarm and coat with mushroom mixture. Sprinkle with chopped parsley and serve immediately with lemon wedges.