For a lower-calorie dish, in the sauce use 1 cup water and 1 cup nondairy milk, and/or decrease the amount of cashews from ½ cup to ¼ cup. You can also omit or reduce the grated cashews on top.
If you have a high-sided (deep-dish) 9x13 casserole dish, this would be a great use for it. The layers can get pretty high, but if using a regular 9x13 dish (not deep dish), just press down on the layers with your hands before placing the last layer of potatoes.