In a measuring jug, mix together the remaining tofu steak ingredients. Pour over the sliced tofu and gently stir to make sure all the tofu is coated in the sauce.
100 ml boiling water, 1 x vegan stock cube, 2 tablespoon dark soy sauce, 1 tablespoon dark brown sugar, 2 teaspoon marmite, 1 tablespoon nutritional yeast, 1 clove garlic, 1 teaspoon mustard powder, 2 tablespoon vegetable oil, 1 tablespoon vegan Worcestershire sauce, 1 teaspoon ground black pepper, 1 teaspoon flaky sea salt