Swordfish is great for entertaining - sear it just rare and then
warm it in the oven to serve. Prepare the agrodolce sauce ahead if
you have the chance; simply toss the pine nuts, lemons and dill in
at the last minute.
Preheat oven to 170C. For agrodolce sauce, heat vinegar and sugar in a small saucepan to a simmer over medium heat, stirring to dissolve sugar. Place onion in a bowl, pour vinegar mixture over, add currants and set aside to steep (5 minutes).
Meanwhile, roast pine nuts on an oven tray, shaking pan occasionally, until golden (4-6 minutes). Transfer to onion mixture along with lemon segments and set aside until ready to serve, then stir in the dill.
Heat a barbecue or char-grill pan over high heat. Brush swordfish steaks with olive oil, and seaon to taste, then grill, in batches if necessary, turning once, until golden and cooked medium-rare (1½-2 minutes each side, depending on the thickness of the fish). Serve warm with agrodolce spooned over and lemon wedges to the side.