Chicken schnitzel: preheat your oven to 450 degrees F (230 C).

First, you need to butterfly your chicken breast until it's in two pieces. Butterflying cuts the chicken breast parallel with your cutting board so that you will have a flat, thinner piece of chicken. Here's a short butterflying tutorial if you've never butterflied a chicken breast before. After you've butterflied the chicken, go ahead and cut the large chicken piece in half so that you have two thin cutlets. 

Cover the cutlets with plastic wrap or even better, a large zip-top bag that you have laid on top of the chicken. Using a meat mallet or a heavy pot, pound the chicken through the plastic to attempt to flatten each piece of chicken until it is less than 1/4-inch thick. This might take some effort and it will expand the width of your chicken piece considerably. After the chicken has all been pounded, cut each cutlet into pieces that are around the size and shape of your bread. You should be able to get 3 to 4 bread-sized, quarter-inch thick cutlets out of one chicken breast. 

Set up your chicken dredging station. You will need three bowls or large plates for this. 

The first bowl will contain all-purpose flour. Add 1/2 teaspoon salt and 1/2 teaspoon black pepper to the flour. The second bowl will contain 2 whole eggs and mayonnaise. Whisk to combine well. The third bowl will have Panko breadcrumbs, 1 teaspoon salt, 1/2 teaspoon black pepper, and 2 teaspoons of paprika. whisk to combine. 

Line a sheet pan with aluminum foil. Spray the foil with cooking spray, this is where your chicken will go when you have coated it in breadcrumbs.

For each chicken cutlet, coat with flour in the flour bowl, then dip into the egg mixture (ensuring that it's fully coated everywhere) and finally press into the breadcrumb mixture until each piece is fully coated. Place on the cooking spray sprayed aluminum foil. 

Spray the top of each piece of chicken with cooking spray, this will help the chicken get a tiny bit of color and crisp up better. 

Bake for 6 minutes, remove from oven, and flip each chicken cutlet. Spray the top side of the chicken again with cooking spray. Bake for an additional 5 minutes. 

Sandwich assembly: grab two slices of bread and apply mayonnaise to one side of each piece (if using).

Top the mayonnaise with two to four of your chicken cutlets. If you're making two sandwiches, use half of your cutlets on each sandwich.

Top the cutlets with iceberg lettuce, tomato slices, and the second slice of bread. Serve and enjoy.