1. Pat the steaks dry with paper towels and rub with the oil. Set aside until needed.
2. Rub: Heat a dry pan on the stove top and toast the coriander seeds until fragrant. Grind the seeds in a mortar. Add to the rest of the ingredients and mix well. Sprinkle over the steaks and rub in well.
3. Sauce: Heat the oil in a large pan and fry the garlic until fragrant. Add the mushrooms and stir-fry until done. Add the brandy and peppercorns and sprinkle the flour over. Mix well.