1. Whisk lard with the boiling water in a large bowl until completely melted. Add the salt. Refrigerate for about 30 minutes, stirring occasionally.
2. Add 1 L (4 cups) flour and mix with a wooden spoon. 
3. Gradually stir in remaining flour to make the dough still sticky but workable. Refrigerate for about 30 minutes.
4. Preheat oven to 220°C (425°F).
5. Mix together the berries and sugar in a saucepan, and simmer over medium-low heat until fruit is stewed.
6. Dissolve cornstarch in a little cold water and add to the fruit mixture. Bring to a boil and simmer 2 to 3 minutes, stirring constantly. The mixture will thicken slightly. Set aside.
7. On a clean, floured surface, roll out a pastry disc that's a little bigger than a 23-cm (9-in.) pie pan. For best results, use a glass pie pan. The pastry should be about 0.3-cm (⅛-in.) thick. 
8. Place dough in pie pan being sure to leave a small overhang all around. Prick bottom of pie shell all over so the heat can escape while baking.
9. Add reserved fruit filling to the pie shell. 
10. Roll out a second piece of dough and cut into 1.5-cm (½-in.) strips. Criss-cross the dough strips on top to make a lattice crust. Trim off excess pastry. Using a fork or your fingers, seal dough around top of pie pan. 
11. Mix together egg white with 15 mL (1 tbsp.) water; brush mixture over dough. 
12. Bake in centre of oven for 20 minutes. Reduce oven temperature to 180°C (350°F) and continue baking for 15 to 20 minutes, until the crust is golden brown and the liquid bubbling. 
13. Let pie sit until filling thickens, about 1 hour, and then serve. 

Chef’s secret

Always have a pie in the freezer that’s ready to bake if unexpected guests drop by. Prepare the pie as you would, being sure that the filling is chilled before adding it to the pie shell. Hermetically seal and freeze the unbaked pie. When needed, pop the frozen pie into the oven. It will need to bake a bit longer, about 30 minutes at 220°C (425°F) and then another 20 to 25 minutes at 180°C (350°F).