The finished recipe. Tuna Steak with Chimichurri and Sweet PotatoIngredients 1 to 6. 160 g Tuna steak (Weighed raw.). 200 g Sweet potato (Raw, peeled weight.). 10 g Olive oil (Most of it goes into the chimichurri, which is an oil-based sauce. Ten grams is under a tablespoon.). 1 clove, about 3 g Garlic. A large handful, chopped finely Fresh parsley. One teaspoon Dried oreganoIngredients 7 to 8. One tablespoon Red wine vinegar. A pinch Chilli flakesStep 1. Heat the oven to 220°C. Cut the sweet potato into wedges, toss with a teaspoon of the oil and salt, and roast for thirty minutes, turning once.Step 2. Stir the parsley, oregano, grated garlic, vinegar, chilli flakes, the rest of the oil and a pinch of salt together. Leave it to sit while the potatoes cook.Step 3. Season the tuna and grill it under a hot grill, or in a smoking-hot griddle pan, for two minutes a side.Step 4. Rest for two minutes, slice, and spoon the chimichurri over with the wedges alongside.