Peel the potatoes and cut into 3cm chunks. Put the potato in a medium saucepan of cold salted water and bring to the boil. Reduce the heat to medium and cook for 12-14 mins until tender. Drain. Return the potato to the pan and cover to keep warm.
Step 2 — Prep ingredients
Meanwhile, thinly slice the onion. Finely chop half the rosemary leaves*, discarding the stems. Combine the rosemary and 1 tsp sea salt flakes (see cooking tip) in a bowl, massaging with your fingertips to release the aromatic flavour.
Step 3 — Prep salad ingredients
Halve the cucumber lengthwise and thinly slice on an angle. Slice the apple. Put 3 tsp extra virgin olive oil and 1½ tsp white wine vinegar in a large bowl, season with salt and pepper and whisk to combine. Add the apple to the dressing and stir to coat.
Step 4 — Cook steaks
Heat a medium frypan over high heat until hot (see cooking tip). Drizzle the steaks with 2 tsp extra virgin olive oil. Reduce the heat to medium-high and cook the steaks for 2-3 mins each side for medium-rare, or until cooked to your liking. Remove from the pan, season with some of the rosemary salt and pepper and keep warm.
Step 5 — Make onion gravy
Heat the same pan over medium-high heat. Cook the onion, stirring occasionally, for 3 mins or until golden. Add the gravy powder and 160ml (⅔ cup) water and cook, stirring, for 1 min or until the gravy boils and thickens. Season with pepper.
Step 6 — Mash potato and serve
Mash the potato until smooth. Add 20g butter, season with salt and pepper and stir to combine. Add the cucumber and spinach to the apple mixture and gently toss to combine. Divide the mash, steaks and onion gravy among plates. Serve with the remaining rosemary salt and apple salad.