In a large pan melt butter over medium heat. Add grated yellow onion and sauté for about 2 minutes then add minced garlic and continue to sauté for an additional minute. Add fresh spinach to pan and cover with a lid. Allow spinach to wilt for about 3 minutes without stirring. Once the wilt has occurred either cut or stir spinach to break it up.

Place milk in a large glass and add flour. Use a whisk and whip half and half milk and flour until completely combined so the mixture is smooth and there are no lumps. Pour mixture over wilted spinach and cook over medium heat until the half and half milk has reduced by half. Sprinkle freshly grated parmesan cheese over creamed spinach. Cover with lid and reduce heat to simmer. Cook on low until cheese has melted. Serve and enjoy!