@Desert-Dan not to state the obvious, but there are 2 major “schools” of lasagna – béchamel and ricotta (which also tend to align as Italian-Italian vs Italian-American).
Here’s a nice article about lasagna bolognese (Marcella Hazan’s is a lovely version of it) using fresh pasta – you could replace the tomato bolognese with a white mushroom bolognese, or a vegetable ragu without tomatoes.
Ricotta lasagna is sturdier, and dried noodles are great in it (either no-boil or pre-boil). If you want to control the salt, ricotta is easy to make at home (it’s just curdling milk and straining).
(1) What kind of shredded cheese do you use
Grated parm or pecorino in the béchamel version, whole milk mozzarella in the ricotta version.
(2) Do you mix an egg in with the ricotta cheese?
No – when I make vegetable lasagna it’s for vegetarians who don’t eat eggs. You can add a bit of cornstarch to help it firm up if you want.
(3) What vegetables do you use?
For the ricotta version, diced onion, bell peppers, mushrooms, and well-drained frozen spinach mixed with the sauce.
For vegetarian béchamel lasagna, a variety of mushrooms (like the SK one @linguafood posted).
Another idea is to add layers of long-sliced zucchini or squash or eggplant instead of diced. Roast first so the liquid doesn’t make your lasagna soggy (since you can’t salt in this case).
(4) How many layers are in a traditional vegetable lasagna?
As many as you want. I like more vs less. You can get more fresh pasta layers in a pan than dried, but make sure you have enough of the other layer components.
(5) Any helpful tips or tricks?
One of the nicest vegetable lasagnas I’ve eaten is also the quickest – a friend microwaves all the vegetables instead of sautéing or roasting, which I was shocked by, but I had already eaten and loved the end product before I knew the shortcut!
Roasted red peppers can stand in for tomatoes (though a white lasagna is perfectly lovely). I love the idea of butternut squash too, but I’d roast it to intensify.
If you skip the parm and cut back cheese in general for salt, you can use nutritional yeast and/or cashew paste in the béchamel (soak cashews, drain and puree).
Lasagna roll-ups are easier to assemble, portion, and freeze than a big tray.