This burger is super simple to put together and packs a lot of flavour thanks to the pasta sauce and the great umami flavour of the portobello mushroom. I went for a more Italian flavour profile with the spinach and mozzarella-style vegan cheese. This burger is super juicy and satisfying, even your omnivorous friends will want one.
I used a mini George Foreman grill because I live in an apartment and that's all I've got, but if you have an actual grill, you should totally use that for extra smokey deliciousness.