Wash and clean the spinach. Saute the garlic and onion in a deep pot. Add the spinach (bhagi) to the pot, mix and allow to cook until the leaves are soft.
Make the white sauce. Over a low flame, melt the butter, stir in the flour, and add the milk. Mix, preferably with a fork to ensure that the flour don't lump together. Continue to boil until the milk gets thick. Remove immediately from the flame.
Boil the pasta. Drain when cooked and set aside to cool.
Grease the dish and line it with the pasta. Add the white sauce (if you are placing tomato sauce, then add it now), layer the spinach, then the cheese, and then another layer of pasta. Continue until done.
Note: you will have about three layers when done. You may still have some spinach, this can be placed on the top as well before the last layer of cheese. Bake for 40 minutes at 250 degrees Fahrenheit.
Allow to cool before serving.