Mix the butter with the garlic, parsley, and lemon zest until thoroughly combined. You can use a hand mixer or use a fork.
Form into a log shape about 4 inches long on a piece of parchment paper. Roll the paper till the butter is covered and twist the ends to hold it tightly. Place in the freezer for 30 minutes to firm it up quickly. If you do this.
Once your chicken is pounded into about ¼ inch thick pieces, lightly salt it.
Remove the butter from the freezer and cut it into 4 pieces.
Place 1 chicken on a piece of plastic wrap (smoothest side down) and put one piece of butter in the middle.
Roll the chicken up first by starting on one side. Fold the sides in as you roll and roll the chicken tightly.
Roll the plastic wrap up around the chicken tightly and twist the sides to make it even tighter.
Freeze the rolled chicken for 45-60 minutes. This will ensure the butter doesn’t spill out when cooking.
While the chicken firms up in the freezer, put the flour, salt and pepper in one shallow bowl, the beaten eggs in another shallow bowl and the panko in a third shallow bowl. Preheat the oven to 400 degrees and line a baking sheet with parchment paper. Place a rack on top of the baking sheet for best results.
Once the chicken is firmed up in the freezer, add the oil to a pan so that the oil will cover half the chicken when placed in it. Heat the oil to medium high. Ideally your oil temperature will be about 350 degrees.
First roll a piece of chicken in the flour, brushing off any extra flour. Dip the floured chicken in the egg and then roll in the breadcrumbs. Repeat with remaining pieces of chicken.
Fry the chicken for about 3 minutes per side, until golden brown on both sides.
Place the chicken on the prepared baking sheet on the rack. Bake for about 15-20 minutes until the chicken is cooked through. To check this easiest, use a thermometer. When the center reaches 165 it is fully cooked. Do not overcook.
Let the chicken rest for 10 minutes before slicing, for best results.