Start by peeling the sweet potato. Use a box grater to grate the sweet potato into hash brown sized pieces.
Heat one tablespoon olive oil in a large skillet over medium-high heat. Once hot, add the sweet potato and shredded collards. Sprinkle with ¼ teaspoon salt. Cook for 5 minutes, stirring occasionally. The collards should be vivid green and slightly wilted and the sweet potato will be softened but not cooked through.
Meanwhile, add the eggs, milk, remaining ¼ teaspoon salt, garlic powder, onion powder and black pepper to a medium bowl. Whisk together for at least 30 seconds.
Lightly spray an 8x8 or two quart casserole dish with cooking spray. Add the collards and sweet potatoes and spread into an even layer. Pour the egg mixture on top. Top with the shredded cheese.
Bake uncovered at 350 degrees F for 35 minute, or until a knife inserted in the center comes out clean. Another way to tell that the casserole is done is when the eggs are golden but not brown, especially at the edges.
Remove from the oven. Slice and serve garnished with freshly chopped parsley and sliced scallions.
Leftovers: You can keep leftovers refrigerated in a closed container for 3-4 days.
Make-ahead instructions: Assemble the unbaked casserole in the baking dish and cover with foil or a lid. Refrigerate until ready to use in the morning. I recommend waiting no more than 24 hours after assembling. You may need to bake the casserole for an extra 5 minutes.