Prepare the shiso leaves by trimming the stems. Mash the umeboshi into a paste.

Roll the melting cheese slices tightly from one end.

Remove the tendons from the chicken tenders. Make a cut in the center and open them like a book. Cover with plastic wrap and lightly pound to flatten. Season with salt and pepper.

Place half of the umeboshi paste, shiso leaves, and cheese on two chicken tenders. Cover with the remaining chicken tenders and press lightly.

Spread mayonnaise on both sides of the chicken and coat with breadcrumbs. Repeat for the second piece.