Cut the mozzarella into 1-inch x 1/3-inch x 1/3-inch sticks (3cm x 1cm x 1cm).
Cut each chicken tender into 3 pieces about 1 1/2-inches in length.
Use a sharp paring knife to cut a pocket into each piece of chicken lengthwise. You want to cut almost all the way through the chicken.
Stuff he mozzarella into the pockets you just making sure the cheese goes all the way into the chicken (but doesn't come out the other side).
Sprinkle the chicken with salt and pepper to season.
Put the flour into one bowl. Break the egg into a second bowl and beat until uniform in color. In a third bowl, add the panko, parmesan, and parsley and mix to combine.
Dust all of the chicken with a generous coating of flour, rolling each piece around to ensure you get a thick even coating of flour.
Then use one hand to dip the chicken in egg, and then transfer it to the bowl of panko.
Use your other hand to roll the chicken nuggets around in the panko. This will keep your hands from getting breaded along with the chicken.
Prepare a wire rack lined with two sheets of paper towels.
Add 1-inch of oil to a heavy bottomed pot and heat to 340 F (170 C).
Fry the chicken on one side until the panko starts to brown around the edges and then flip and fry the other side until browned. Be careful not to over fry the chicken or the mozzarella will come spewing out and the chicken will become dry.
In all likelihood some of your nuggets will leak a little mozzarella so keep a small mesh skimmer handy to skim off any bits of mozzarella that escapes.
Serve hot with a bowl of basic tomato sauce.