Step 1

Preheat oven to 200°C. Wrap garlic in foil. Roast for 30 minutes. Unwrap. Set aside for 5 minutes to cool. Halve horizontally.

Step 2

Squeeze garlic flesh into a bowl. Stir in the mayonnaise, sour cream and chives. Cover with plastic wrap. Place in the fridge.

Step 3

Use unwaxed white kitchen string to tie the beef at 4cm intervals. Place combined mustard and tarragon in a bowl. Rub over beef. Place in a roasting pan. Roast for 35 minutes for medium-rare or until cooked to your liking. Cover. Set aside for 10 minutes to rest.

Step 4

Thinly slice the beef. Place on a platter. Serve with aioli.