Clean and cut the carrots and celeriac into julienne strips 3 cm (1¼ inches) long and ½ cm (¼ inch) wide, and put them in a sauté pan. Add the garlic, and peppercorns and cover with the 400 ml (¾ pint) olive oil. Bring to the boil and allow to simmer gently for 10 minutes, cool, remove and drain the julie