This is a Nagi Maehashi recipe from her book, RecipeTin Eats Cookbook: Dinner.
The recipe is also available online at the Tin Eats website.
What makes the tenderloins so good is the mayonnaise and mustard based batter, and oven toasting the panko bread crumbs before applying.
I served them with creamy butter and cream mashed potatoes and a cucumber, rocket and gem lettuce salad with a white balsamic and olive oil dressing.