Mix the bilberries and half the sugar. Core the apples and bake until tender. Scrape out the pulp and sweeten with the remaining sugar and mix with the bilberries.
2.
Butter and line a pie plate with pastry. Put in the bilberry filling and cover with pastry. Brush with egg white if using shortcrust pastry. Sprinkle with a thin layer of sugar. If using puff pastry glaze with an egg glaze.
3.
Bake in a hot oven to set the pastry - gas 6 to 7, 200 - 220 Celsius (400 - 425 F) - then lower the heat to moderate (gas 4, 180C, 350F) to cook the fruit.
