Heat olive oil in a frying pan, add chopped onion and garlic and cook for 3 minutes or until fragrant. Add spinach and nutmeg and cook until spinach is wilted, season with salt and pepper.
Add a tablespoon of butter to wilted spinach and transfer shirataki noodles to the same pan. Pour in beaten egg and stir until the egg is set. Stir in chopped dill and mint.
Divide between serving plates and top with crumbled feta. Sprinkle with grated Grana Padano and more black pepper if needed.