Place tomatoes on baking paper on a baking tray and roast at 220°C/450°F/Gas Mark 6 until they just begin to pop. Or, heat up a frying pan and cook them in a little oil, shaking occasionally until they pop. Set aside.
Cook potatoes in lightly salted water, drain and slice
To make salsa verde, mix herbs with remaining olive oil, wasabi and a pinch of salt. Mix well, then mix in remaining lemon juice.
To serve, brush tongue with a little oil and grill or sauté until warmed through. Mix marinated onion with potatoes and divide between six plates. Lay tongue on top, then scatter on tomatoes and drizzle on the salsa verde, or serve it in a bowl.
Buy a raw pickled or brined ox tongue (or you may want to use several lambs’ tongues), place in a bowl of cold water and leave for 1 hour. Change the water and leave for another hour. Do this once more so the tongue has soaked for a total of 3 hours.
Drain and place in a large pot with
Leave to cool in the liquid and peel when cooled. Store in the fridge for up to 5 days.