Grilled Rare Tuna Steak with Fennel, Green Garlic and Roasted Garlic Aïoli

This is a wonderful, easy-to-prepare number for a summer lunch or outdoor dinner that blends the subtle flavour of green garlic (immature garlic picked before the cloves have developed) with the aniseed taste of fresh fennel in a gently stewed lemon emulsion that complements the oiliness of the tuna and aïoli. The best results are achieved by minimal cooking. Well-cooked tuna belongs in a can, so if you go to the bother of buying a beautiful piece of fresh tuna, do it justice and cook it ra