Spinach Alfredo sauce

I came up with my own recipe for a spinach alfredo sauce.

Ingrediants:
1 stick butter
3 tablespoons flour
1/2 cup shredded M Jack cheese
4 cups finely chopped baby spinach
1 med sized finely chopped red onion
2 green chillies finely chopped
4 cups whole milk
salt

Melt the butter in a flat saucepan. Cook the green chillies and red onion until fully cooked. The onions should look a pink and translucent. Add the flour while stirring. Slowly add the milk, make sure no lumps are formed. On a medium flame bring to a boil. Add the spinach and salt. Cook for 1 minute. Add the cheese. Cook till the consistency of the sauce is what you like. I like a running sauce, so I didn't boil it much more. But if you like a thick creamy sauce. Cook it for about 3-4 minutes.

Hint for leftover: Add some milk or water before heating the sauce and adding it to the pasta.