Boil enough water(3-4 cups) in a pot adding little salt and cook the pasta for 10-12 mins or till cooked to desired consistency.
While the pasta is cooking, heat another pan and melt the butter.
Add the whole wheat flour to the melted butter and roast for 2-3 mins.
Add the milk to the roasted flour, little at a time, stirring continuously so that there are no lumps.
Once the entire milk is added, bring it to a boil and add salt and pepper.
Add the chopped spinach and grated cheese and bring to another boil.
Once the pasta is cooked, add it to the sauce and give a too mix.
Keep the pan covered and cook on low flame for another 3-4 mins.
Serve the pasta ,garnishing with some more grated cheese.