Castello Havarti Tuna Melt Cakes Recipe

For the tuna melt cakes:
5 to 6 medium russet or gold potatoes
6 ounces sustainable tuna in water, drained
Juice and zest of 1 large lemon
1 tablespoon yellow mustard
2 tablespoons mayonnaise
2 tablespoons fresh chives, finely chopped
1/2 cup canned or frozen corn
1 teaspoon salt
1/4 teaspoon freshly ground black pepper
1-1 inch cubes Castello light havarti cheese
1 egg, beaten
1 1/4 cups panko breadcrumbs
1 cup vegetable oil

For the lemon mayonnaise:
1 cup mayonnaise
Juice of 1/2 lemon