Beat the egg in a measuring cup. Add the vinegar and enough cold water to make one cup of liquid.
In a large bowl combine the flour, baking powder, salt, and brown sugar. Cut the lard up into small cubes, and add to the dry ingredients. Blend with two knives, or a pastry blender, until the mixture is crumbly. Add the liquid ingredients, mixing with a knife. Do not use your hands as it tends to soften the lard too much. Add additional water, if required, to make a soft ball of dough. If the weather is warm, refrigerate your dough for 1/2 hour to chill it before rolling. Warm dough doesn't roll as well, and requires too much flour, which makes it less flaky.