Vegan kohlrabi and fennel gratin

inspired by this

1 c cashews
1-1.5 c hot broth
1 T earth balance
1/2 onion, thinly sliced
1/2 large fennel bulb, thinly sliced
4 red potatoes, thinly sliced
3 small kohlrabi bulbs, peeled and thinly sliced
4 medium-small criminis, thinly sliced
~2/3 c leftover mushroom gravy (wasn't actually vegan but could have been)
1/2 t paprika
1/2 t tarragon
1/4 t nutmeg
generous grating of black pepper
toasted breadcrumbs

Preheat oven to 375F. Combine cashews and broth in small bowl and let soak for a while. Get all the veggies sliced and ready to go. Melt the earth balance in a large pot and saute the onion and fennel, then add the other veggies and gravy and cook for a few minutes. Meanwhile, drain the cashews (reserving the broth) and grind until smooth in a food processor. Add the broth a little at a time, trying not to make the food processor spit liquid all over, until a desired creamy consistency is desired. Stir the cashew cream and spices into the veggies. Transfer to a greased 9" square pan. Bake for 20 min, sprinkle on the breadcrumbs, and bake for another 10-15 min until bubbly and the potatoes are done. While the gratin is baking, cook up the kohlrabi greens (washed, destemmed, and chopped) with some garlic, arugula, and pine nuts, and serve that on the side. First vegan cashew experiment: totally a success!