A tip for all those cooks out there:
If you’re ever making tetrazzini (vegetable, in my case), make sure you add the flour to the sauce so that it actually thickens up and becomes sauce, not just a casserole dish full of pasta, vegetables, broth and hot half and half.
In short: Read your recipe carefully and completely.
(Despite this mistake, the pasta and vegetables were still edible, and so we still had them for dinner. Wasn’t really tetrazzini though.)