Begin by freezing the firm tofu overnight to develop a denser texture. Once frozen, defrost and press it between paper towels to remove excess moisture. Slice into two thick cutlets.

In a small bowl, mix vegetable stock and marmite until dissolved. Brush this marinade over each tofu cutlet and let it sit for about 10 minutes.

Combine all-purpose flour with cold water to create a smooth batter. Stir until there are no lumps.

Dip each marinated tofu cutlet into the batter, ensuring an even coating. Then transfer to a bowl filled with panko breadcrumbs to stick well.

Heat vegetable oil in a deep pot to 340°F (170°C). Fry the breaded tofu cutlets for about 6-8 minutes until golden brown and crispy. Turn halfway through.

In a saucepan, combine sake and apple juice, simmer for about 5 minutes, then stir in the remaining katsu sauce ingredients. Cook for another 3-5 minutes until thickened.

Remove the Tofu Katsu from oil, place on paper towels to drain. Allow to cool slightly and slice into bite-sized pieces. Plate with katsu sauce on top.