Prepare the Chicken: Pound or butterfly chicken until thin. Set up three bowls: one with flour and optional protein powder, one with beaten eggs, and one with breadcrumbs, Parmesan, paprika, garlic powder, onion powder, parsley, salt, pepper, and lemon zest. Dredge chicken in flour mixture, then egg, then coat in breadcrumb mixture.
Cook the Schnitzel: Place on a lined rack and spray both sides with olive oil. Air fry at 400°F for 10–12 minutes, flipping halfway, or bake at 425°F for 16–18 minutes, or pan-fry lightly until golden and cooked through. Finish with a squeeze of lemon.
Make the Mash: Boil potatoes in salted water until fork-tender, about 14–16 minutes. Drain and mash with Greek yogurt, butter, milk, green onions, salt, and black pepper until creamy.
Roast the Asparagus: Toss asparagus with olive oil, garlic, salt, pepper, and lemon slices. Roast at 425°F for 10–13 minutes until tender and slightly charred.
Serve: Plate schnitzel with mashed potatoes and asparagus. Garnish with extra lemon if desired.