Ziti with Broccoli and Blue Cheese

So I tried this out of the student cookbook Jody got me for Christmas. I love blue cheese and actually like broccoli, despite being convinced otherwise for many years. It's a pretty simple recipe, though this is the first time I've ever used flour to make a sauce. A whole new world may have opened up.

6 oz. Macaroni (or ziti in this case)
8 oz. Broccoli florets
Knob of Butter (I had to use the Internet to figure out how much this is supposed to be, and I'm still not entirely sure.)
1 T Flour (I've never bought flour before, but there are 32 more ounces where this came from, so watch out.)
7 oz. Vegetable stock (I used chicken stock instead.)
Grated rind and juice of half a lemon (I skipped the rind, as I just had a plastic container of lemon juice.)
2 oz. crumbled blue cheese

Cook pasta for 7 minutes and then add broccoli to water and cook for another 5 minutes.
Heat butter in a small pan, add flour, and beat together with a wooden spoon until smooth.
Gradually stir in stock and bring to a boil.
Add lemon juice and simmer gently for one minute.
Put drained pasta and broccoli in a dish and pour over the sauce.
Sprinkle over the blue cheese and toss well.

Surprisingly, it wasn't that bad, though I had some serious doubts before starting to eat. It was rather soupier than I would have liked. I suspect this was because the broccoli was overcooked and still a bit soggy after I drained it. (Five minutes over a gas stove might be too long for broccoli.) Any other ideas?