I used a wide variety of cheeses; you could use other cheeses such as goat cheese, Gruyère, Asiago, Munster or even blue cheese.
To make béchamel sauce, I always start with all the ingredients at the same temperature, so make sure to heat the milk in the microwave for about 2 minutes (or in a saucepan), so it's warm. If you get lumpy pieces in the sauce, don't hesitate to use a hand blender.
Vegetarian protein crumble is available in the produce aisle of many supermarkets such as Safeway. The texture is very similar to ground beef.