Heat your oven to 200°C/Fan 180°C/Gas 6. Scrub the potatoes and chop them into chips about as thick as your little finger. Pop them in a bowl and toss with ½ tbsp oil and a pinch of salt and pepper. Spread out on a baking tray and roast for 30 mins till the chips are tender and browned.
Unwrap the steaks and pop them on a plate. Peel and finely grate the garlic. Rub the garlic into the steaks with 1 tsp of the cumin seeds, a pinch of salt and pepper and 1 tsp olive oil. Set aside.
Peel and coarsely grate the carrots. Chop the leaves off half the radishes and shred them. Coarsely grate the radishes. Pop the veg in a bowl. Grate in the zest from the lime. Add a pinch of salt and pepper. Squeeze in the juice from half the lime. Add 1 tsp olive oil and toss to mix. This is your Mexican slaw. Set aside.
Halve, peel and thinly slice the shallots. Set a large frying pan over a high heat and warm it for 1 min. Add the shallots (no oil needed). Turn in the pan for 2-3 mins till charred. Add 1 tsp cumin seeds and a squeeze of juice from the remaining lime half. Tumble onto a plate. Set aside.
Keep the pan on the heat. Add the steaks. Cook for 30 secs-1 min on each side for rare to medium steaks. Cook a little longer for more well done steaks. Pop them on a plate or board and loosely cover with foil. Set aside to rest for a few mins.
While the steaks rest, finely chop the coriander leaves and stalks. Add them to the Mexican slaw and toss to mix. Taste and add more salt and pepper if you think it needs it.
Halve the avocado. Scoop out the stone. Scoop the avocado flesh out of the skin onto a plate. Gently mash it with a fork. Dust with a pinch of salt and pepper. Squeeze over the remaining lime juice.
Serve the steaks with the Mexican slaw, the mashed avocado, charred shallots and chips.