Peel and crush the garlic and finely chop the mint. Blend with the juice of the lemon and slowly add the oil to emulsify. Season to taste.
Heat a griddle pan until very hot. Rub the tuna loin with the olive oil and season with Maldon sea salt and lots of ground black pepper.
Cook the tuna loin on all sides for 30 seconds. Remove from the heat.
Toast the cashews in a hot oven until golden all over. Finely slice the shallots and fry in the oil in a medium hot pan until golden. Separate the broccoli into small florets and steam until tender but with some bite - it should still be bright green.
Drop the quinoa into boiling water and cook for just a few minutes - it should retain some texture. Drain, then toss everything together gently with the dressing. Serve warm or at room temperature, alongside slices of the tuna.
«This makes an excellent cold lunch dish - you can prepare it the night before.»