Creamy Shell Soup

I first made this a few weeks ago...okay, it might have been November, I can't remember...and my husband absolutely loved it. It's easy enough to make, even if you do let the pasta get over-cooked.

3 or 4 boneless, skinless chicken breasts
1/2 small onion, diced
1 can navy beans
1 (large) can mushrooms, drained (I had actually used fresh ones, because I had some)
6 c. water
3 chicken bouillon cubes
1 bay leaf
spices: poultry seasoning, chives, coriander, parsley flakes, salt, & pepper.
2 c. uncooked pasta shells (small or medium; either is fine)

Roux: 4 T. butter w/ 4 T. flour & +/- 4 c. milk

1. Dice chicken into 1/2 – 1/4 inch cubes; mince onion; put into stock pot with 6 cups of water. Add seasonings and bouillon cubes.
   
2. Bring to a boil, and add mushrooms and navy beans.
   
3. Once boiling again, add pasta & begin making roux by melting butter in small sauce pan.
   
4. Stir four into melted butter, and cook, adding milk slowly.
   
5. Bring to a boil and watch for it to thicken to a nice rich consistency, then add to stock pot. Stir well to blend.