Season the diced chicken with salt and pepper.
Heat olive oil or butter in a large skillet over medium-high heat and cook the chicken until golden and cooked through, about 5 to 7 minutes. Remove and set aside.
In the same skillet, add more oil if needed and sauté the onion until soft, about 3 minutes.
Add the minced garlic and cook for 1 minute until fragrant.
Add the potato gnocchi to the skillet and cook according to package directions until they puff up and brown lightly.
Pour in the heavy cream and chicken broth, stirring to combine, then bring to a gentle simmer.
Stir in the grated Parmesan until melted and smooth.
Add the fresh spinach and cooked chicken back to the pan, cooking a few minutes until the spinach wilts and everything is heated through.
Season with additional salt, pepper, and red pepper flakes if desired.
Serve warm, garnished with chopped parsley or basil if desired.