Preheat oven to 325°F. Blanch the raw turnip slices in salted boiling water for 3 minutes. Remove from water and drain.
Layer bread, turnip slices, onions, cheese in casserole dish: Coat the inside of the casserole dish with olive oil. Place a layer of bread on the bottom of the casserole dish.
Layer on half of the turnip slices in a single layer, season with salt and pepper.
Layer on all of the onions. Sprinkle with half of the cheese. Add another layer of bread, turnips, and cheese. Sprinkle again with salt and pepper.
Bake: Place casserole on top rack of oven. Bake at 325°F for 25 minutes. For the last few minutes, if you want, and you are using a pan (metal or ceramic) that can safely handle broiling temperatures, broil for a couple minutes to brown the top.
Remove from oven and let cool for 10 minutes before serving.
2 medium sized young turnips (about 1/2 pound total), peeled, and sliced 1/8-1/4 inch thin
Extra virgin olive oil
3-4 slices white bread (enough to make two single layers in the pan), crusts removed
A few slices of onion, very thinly sliced, enough to cover the pan in one layer
4 ounces Gruyere cheese or substitute with vegan cheese or make your own cashew vegan cheese
Salt and pepper
8x5 baking pan or casserole dish