Heat milk till lukewarm. Make a starter dough with the milk, 1tablespoon of the flour and the yeast. Let the starter rise for 10 minutes.
Mix remaining flour with 1 whole egg, the cracklings, rum, salt, pepper, melted lard and wine. Mix in the starter, and knead well.
Let the dough rise in a lukewarm place until it doubles in bulk, 30 to 45 minutes.
Roll out the dough on a floured board and fold it. Cover it with a clean cloth and let it rest for 10 minutes.
Repeat the same procedure twice or three times-rolling, folding, resting. Preheat oven to 400°F.
Finally roll the dough to 2-inch thickness. With a biscuit cutter 1½inches in diameter, punch out biscuits.
With a sharp knife score the tops of the biscuits in a lattice pattern. Beat the egg yolk with 1teaspoon water, and brush the glaze on the biscuit tops. Let them rest until this glaze dries, about 10 minutes.
Bake in the preheated oven until golden brown, about 25 minutes.