From: Linda McCartney´s Home Cooking, p. 94
This is a great dish if you have tomatoes you want to use- they are delicious baked in the cheesy sauce. In the recipe, it is described that you should skin the tomatoes, but I think that it works just as well when using the tomatoes as they are.
Vegan and gluten-free:
I have tried using plant-based milk instead of the milk, and have substituted the flour for gluten-free flour- both worked great. In my opinion, it does not need the egg for the sauce to set, so for a vegan version you could just leave it out. Substitute the cheese for 3 tbsp. of vegan “parmesan” but do not mix into the sauce but sprinkle over the casserole just before putting it in the oven.