Cold roast beef is great for a picnic - either slice it before
you head out, or, to keep the beef optimally moist, take a board
and slice it when you reach your destination.
1beef fillet (about 1.6kg), trimmed of sinew 1 tbspolive oilTo serve:watercress sprigsTonnato sauce2eggs, at room temperature185 gmcanned Italian tuna in oil, drained well225 gm(¾ cup) whole-egg mayonnaise50 gm (¼ cup)capers in vinegar, rinsed and finely chopped, plus extra to serve2golden shallots, finely chopped2anchovy fillets, finely choppedJuice of½ a lemon, or to taste
Preheat oven to 250C fan-forced. Place a heavy oven tray in oven to heat. Tie beef fillet at intervals with kitchen string to hold shape, then rub with olive oil and season to taste. Remove tray from oven and place beef fillet on tray, then roast, turning occasionally, until browned and cooked medium-rare (20-25 minutes). Remove from oven, cover with foil and cool to room temperature (30-40 minutes). Wrap tightly in plastic wrap to form a cylinder, then refrigerate until chilled (2-4 hours).
Meanwhile, for tonnato sauce, cook eggs in boiling water until hard-boiled (10 minutes). Refresh, then peel, halve, remove egg yolks (discard whites) and place in a bowl. Add tuna and mash with a fork, then add remaining ingredients, mix well to combine and season to taste with lemon juice and freshly ground black pepper. Sauce will keep refrigerated for 3 days. Serve with sliced beef fillet, watercress and extra capers.