The inhabitants of the French province of Bourbonnais are renowned as hearty eaters, especially fond of vegetable dishes and thick vegetable soups. This pie is a superb ambassador for the region’s cuisine.
To make the shortcrust pastry, sift the flour and salt into a bowl. Using your fingertips, rub in the butter until the flour is evenly coloured and sandy in texture. Make a well in the centre, then add the beaten egg and a tablespoon of water. Mix well, shape the dough into a ball, wrap in plastic wrap and rest in the refrigerator for 30 minutes.