01 - Cook pasta in a large pot of salted boiling water according to package directions until al dente. Drain and reserve 1/2 cup of pasta cooking water.
02 - While pasta cooks, heat olive oil and butter in a large skillet over medium heat. Add onion and sauté for 2-3 minutes until softened.
03 - Add minced garlic to the skillet and cook for 1 minute until fragrant.
04 - Add fresh spinach to the skillet and stir continuously until wilted, approximately 2-3 minutes.
05 - Pour heavy cream into the skillet, bring to a gentle simmer, then stir in grated Parmesan and nutmeg. Simmer for 2-3 minutes until sauce thickens slightly.
06 - Add drained pasta to the skillet and toss thoroughly, adding reserved pasta water gradually to achieve desired sauce consistency.
07 - Adjust seasoning with salt and freshly ground black pepper according to preference.
08 - Transfer to serving dishes immediately and garnish with extra Parmesan cheese and a sprinkle of black pepper.