Slice the chicken breasts in half, season with salt and pepper, and tenderize with a mallet.
Melt butter in a pan, add onion and shallot, and sweat for 7 minutes.
Add carrots and sauté for 3-4 minutes.
Add garlic and ginger, sauté for 2 minutes.
Add grated apple, tomato paste, honey, salt, pepper, and flour, and cook for 1 minute.
Add chicken stock, MSG, and Worcestershire sauce, and bring to a simmer.
Add curry cubes and simmer for 5-10 minutes, then blend until smooth.
Bread the chicken by coating in flour, egg, and panko.
Fry the chicken in vegetable oil at 335°F until golden brown and crispy, about 4-5 minutes.
Let the chicken rest for 3-4 minutes, then slice.
Serve the chicken katsu with the curry sauce, sushi rice, furikake, pickled red cabbage, and spring onions.
