Penne pasta with asparagus in bechamel sauce

The thing about recipe books is, they always use words that sound very fancy, which finally turn out to be  simple, ordinary items (wait....sounds familiar- buttermilk anyone??)...
I had always seen 'bechamel sauce' in many recipes, but did not know what that meant.  So when I googled it, I found that this was just a normal white sauce made with butter, flour and milk. And that's the sauce that Amma makes for various dishes- including au gratin (yummy!) and mushrooms on toast- (double yummy!). Mommie- recipes please:)

Anyway, so this pasta is what I made a few nights ago. 

Ingredients:
Penne Pasta
3 tbsp Olive oil
2 tbsp flour
1.5 cups milk
cayenne pepper- a pinch
1 red onion- cut into strips (I realized later that it may have worked better if the onions had been chopped into small pieces)
1 yellow pepper- cut into strips
5-6 asparagus- cut at about 1" from the bottom, a bit higher if they have become drier

salt & pepper to taste

1. Cook the pasta according to the directions on the package
2. Meanwhile make the sauce. To the olive oil, add the onions and let it cook until translucent.
Reduce the heat, and now add the flour and let it cook into a smooth, bubbling paste, ~3 minutes (similar to the texture of wet sand).

3.  Whisk milk into this mixture and keep whisking until it forms a paste with no lumps. Bring to a boil and reduce the heat to very low. Let it simmer on low heat for about 10 minutes. Add the cayenne pepper at the end of 10 minutes.
4. Add the yellow pepper and asparagus. (I am sure it will be good to add more vegetables at this stage, I just didn't have any more that day!)
5. Let the vegetables cook for about 5-10 minutes, or until tender.

6. Add salt and pepper to taste.
7. Now add the cooked pasta. Voila!