Heat olive oil in a large 12-inch skillet over medium-high heat. Add the sliced mushrooms and diced onion. Cook, stirring only occasionally, for 5 to 7 minutes until the mushrooms are deeply browned and the onion is soft. Add the minced garlic and cook for 1 more minute until fragrant.

Add the ground turkey to the skillet. Cook and crumble with a wooden spoon for 6 to 8 minutes until no pink remains and the meat looks lightly golden. Drain any excess fat from the pan.

Stir in the Italian seasoning, salt, and black pepper. Let the spices cook for about 30 seconds to bloom into the meat.

Add the fresh spinach in two or three batches, stirring between each addition until fully wilted, about 2 to 3 minutes total.

Reduce heat to low. Stir in the heavy cream and grated Parmesan until fully melted and a light cream sauce forms. Serve immediately for the best texture and consistency.