Onion Tart

• 900 g/ 2 lb onions, sliced
• 60 g/ 2

First make a shortcrust pastry by putting the flour in a food processor with the chilled butter dice. Whiz to a crumb consistency then add the egg yolk, salt and 1–2 tablespoons of cold water. Work briefly until it balls. Remove, cling-wrap and refrigerate for 1 hour.