1 cup chopped green onions, white and green parts, divided
TO BAKE WHOLE POTATOES: Preheat oven to 400 degrees. Scrub potatoes under running water. Use a metal fork to poke a few holes in each potato. Place on rack in oven and bake for 50-60 minutes, until soft when squeezed. Remove and cool completely or refrigerate for assembling casserole later.
TO ASSEMBLE CASSEROLE: Preheat oven to 350 degrees. Leaving skin on, chop baked, cooled potatoes into 3/4" cubes and add to large bowl. In separate small bowl, add yogurt, milk, Parmesan cheese, 1/2 cup shredded cheddar cheese, dry mustard, garlic powder, onion powder, salt, pepper, cayenne (if using), and 3/4 cup green onions; stir until combined. Pour over potatoes and toss until mixed. Transfer mixture to an oiled or sprayed 3-quart (9x13") clear baking dish. Sprinkle remaining cheddar cheese on top.*** Bake uncovered 45-55 minutes, until lightly browned on top, and edges and bottom are visibly well browned. Remove from oven and sprinkle 1/4 cup chopped green onions on top.
***MAKE AHEAD TIP. You can stop at this point, cover the dish and refrigerate it for up to 1 day in advance. Remove from the fridge a half-hour before you want to bake it, so it warms to room temperature first.
LEFTOVERS? Keep them in the fridge and reheat in the oven, or on the stove top or grill. Try reheating in a skillet on the stove-top in order to restore those crispy, brown parts. Great with breakfast that way. Or, wrap it in a foil packet and reheat it on the grill--it can also get brown and crispy that way.
NUTRITIONAL INFO (for a 2/3 cup serving): 145 calories, 4.7g fat, 19.5g carbs, 2.9gfiber, 6.5g protein; Weight Watchers PtsPlus: 4