Start by washing the fresh mushrooms thoroughly, then slice them evenly to ensure consistent cooking. Rinse the fresh spinach leaves until clean, and chop them roughly. Mince the garlic cloves finely.

In a large skillet, pour 2 tablespoons of olive oil and place it over medium heat. Allow the oil to warm for about 2 minutes, ensuring it shimmers but doesn't smoke.

Add the sliced mushrooms to the skillet, spreading them out evenly. Sauté them for approximately 5-7 minutes until they are well-browned and tender.

Once the mushrooms are nicely sautéed, stir in the minced garlic. Cook for an additional 1-2 minutes until the garlic becomes aromatic and slightly golden.

Next, add the chopped spinach to the skillet, tossing it gently with the sautéed mushrooms. Allow the spinach to wilt for about 2-3 minutes.

Sprinkle salt and black pepper over the mixture, adjusting to taste. If desired, drizzle with lemon juice. Stir everything together for a minute before removing from heat.

Transfer the sautéed mushrooms with spinach to a serving dish. Optionally garnish with grated Parmesan cheese and serve immediately.