Boil a large pot of salted water. Cook the gnocchi until they float (about 2-3 minutes). Drain and toss with olive oil.
In a skillet, heat olive oil over medium heat. Sauté onion until softened (5–7 minutes), then add garlic and red pepper flakes for an additional minute.
Stir in spinach until wilted (3–5 minutes). Add heavy cream and broth; simmer gently for 2 minutes before mixing in feta and half of the Parmesan.
Fold in cooked gnocchi and butter until well coated. Season with salt and pepper, then serve hot garnished with remaining Parmesan.