Separate the egg, putting the white into a mixing bowl and the yolk into a 1-cup (240 ml) measuring cup. To the yolk, add the juice of half a lemon and enough cold water to bring it up the one cup (240 ml) mark. Chill this in the refrigerator while combining the flours. Leave the egg white at room temperature.
Whisk together the flours and salt.
Cut lard into the flour mixture until it is in lumps about the size of peas.
Whisk the egg white until it is foamy.
Add the yolk mixture to the flour mixture and stir about 7 or 8 times.
Pour the foamy egg white over all and stir a few more times until the dry part is just barely all incorporated.
Cover this dough to seal out the air, and chill in the refrigerator for an hour or overnight.
On a well-floured surface (Use any of the flours used in the recipe), roll out the dough for pies or tarts.
I don't recommend reheating this pie crust. It will remain lighter and flakier if served at room temperature. If you've had your pie refrigerated, just pull it out an hour or two ahead to take the chill off.
If you'd like to save some pie crust for more than a few days, just wrap it well and freeze it for up to a few months. Take it out to thaw for a couple of hours before trying to roll it out. Or, thaw it overnight in the refrigerator.
Please note that the nutritional information is for a whole single pie crust, not just one serving.