Preheat oven to 230degC. Line two oven trays with baking paper.
Toss kumara with a drizzle of olive oil on first prepared tray and season with salt and pepper. Bake for about 25 minutes, until golden. Turn once during cooking.
In a bowl, whisk together egg, milk and mustard. Pat chicken dry and cut into steaks. To do this, place your hand flat on top of chicken breast and use a knife to slice horizontally to make 2 thin steaks. Place chicken in bowl with egg/milk mixture and set aside to soak for a few minutes.
Trim ends of beans; dice tomatoes 1-2cm; roughly chop baby kale. Set all aside. Combine all mustard mayo ingredients in a bowl and mix well. Combine crumbs, mild Cajun spice seasoning and salt and pepper on a plate. Shake excess milk off chicken then coat in crumbs.
Heat a drizzle of oil in a fry-pan on medium heat. Cook chicken, in batches, for about 3 minutes each side (depending on thickness), until cooked through. Wipe pan between batches and add more oil as needed. Reduce heat if crumb starts to burn.
While chicken is cooking, place beans on the second prepared tray, drizzle with olive oil and season. Bake (on rack above kumara) for about 4 minutes. Add tomatoes and cook a further 2- minutes. Remove tray and toss through baby kale to wilt slightly.
To serve, divide kumara chunks, Cajun-crumbed chicken schnitzel and veggies between plates. Serve with a dollop of mustard mayo and a lemon wedge to squeeze over schnitzel just before eating.
*To make the Cajun spice mix yourself, combine 2 teaspoons paprika, 1 teaspoon coriander, 1 teaspoon cumin, ½ teaspoon rosemary, ½ teaspoon smoked paprika