Cut cauliflower into large pieces. Boil in a pot of water over high heat until very soft. Drain.
Meanwhile, thinly slice potatoes, chard, mushrooms and onion. I use a mandoline slicer to get a nice thin slice, I slice the chard into shreds with a knife. Set aside.
Once cauliflower is done, make the sauce by placing all ingredients into a blender. Blend until sauce is thick and creamy.
Layer your casserole in a 9 x 12 baking dish as follows, it may look too tall but it will shrink when baked:
about ¾ to 1 cup sauce on bottom of pan (depending on how saucy you like it)
⅓ of the potato slices
½ of the mushrooms
½ of the onions
½ of the chard
another ¾ to 1 cup sauce (depending on how saucy you like it)
⅓ of the potato slices
other ½ of the mushrooms
other ½ of the onions
other ½ of the chard
another ¾ to 1 cup sauce (depending on how saucy you like it)
last ⅓ of the potatoes
top with another ¾ to 1 cup sauce (depending on how saucy you like it)
sprinkle with parmesan of choice
Cover with foil and bake at 400°F (200°C) for 35 minutes. Remove foil and bake another 15-20 minutes or until browning on top. Allow to cool and set before cutting and serving.
Notes
If you are not using a high speed blender you can either soak the cashews overnight or grind them into a fine powder using a coffee grinder.
I made one batch leaving the potato skins on and one with peeling. Both were great.
You can use another green in place of swiss chard, we also make it with spinach but kale would work too.
I like crimini mushrooms because they give a good flavor but white ones would work too.
The sauce may make a little bit more than you’ll need, depending on how saucy you like it.
To make this nut free, use more cauliflower in place of the nuts for the sauce. Use a total of 3 heads and reduce the veggie broth down to 1 cup, add more if it seems too thick, it will just depend on how waterlogged your cauliflower is after boiling. You can also sub in white beans for a thicker sauce or even silken tofu. Sub in cup for cup in place of the nuts for these two options. If using silken tofu, reduce the veggie broth by ½ a cup to start and see if you need more. It may not be as thick and creamy with these subs. I have not tried these but they are things readers have done.
If there is a veggie in here that you don’t like feel free to sub. For example if you don’t like mushrooms, which seems to be the case with some, eggplant would be a great sub.
Tips to prep ahead: Make the sauce and parmesan ahead of time so all you have to do the day of is prepare the veggies and layer. You can even cut all the veggies ahead of time as well to make the day of even faster.