Heat olive oil in a large skillet over medium-high heat. Add sliced mushrooms and diced onion in a single layer. Cook, stirring occasionally, for 5 to 7 minutes until mushrooms are golden brown. Cook in batches if the pan is small to avoid crowding. Add minced garlic and cook for 1 more minute until fragrant.

Add ground turkey to the skillet. Break apart with a spoon into small crumbles and cook for 6 to 8 minutes until fully browned with no pink remaining. Drain any excess fat if needed.

Stir in Italian seasoning, salt, and black pepper. Taste and adjust seasoning at this stage.

Add fresh spinach in two or three batches, stirring after each addition and letting it wilt before adding more. This takes about 2 to 3 minutes total.

Reduce heat to low. Stir in heavy cream and grated Parmesan until the cheese melts and a light creamy sauce forms, coating all the ingredients. Do not raise the heat or the cream may break.

Taste one final time and adjust salt or pepper as needed. Serve immediately straight from the pan.