Season each veal cutlet with salt, pepper and garlic powder. On four of the cutlets, place 1 slice of cheese, 2 spears of asparagus, one slice of prosciutto and another slice of cheese on top. Top each stack with a second cutlet, folding under and pressing the edges together to make a 'sandwich.'
In a shallow bowl, whisk together egg and milk. Place the bread crumbs on a plate. Dust both sides of the veal sandwich in flour. Dip each one in the egg mixture then coat with bread crumbs. Place on a plate and refrigerate for 30 minutes.
Preheat the oven to 180 degrees C. Heat olive oil in a large cast-iron frypan over medium-high heat. The frypan should be large enough to hold all four sandwiches. Brown the veal on both sides, about 5 minutes per side. Add the onion and red capsicums then cook over medium heat until they are translucent. Pour in the wine and simmer until the alcohol has cooked away - it will no longer smell as strongly. Pour in the chicken stock then add the mushrooms.
Place the frypan and its contents into the preheated oven. Bake for about 30 minutes or until the internal temperature of the veal has reached 70 degrees C. The sauce should also be reduced by about half.