Crumble the yeast into a bowl, add 1 teaspoon of sugar, 2 tablespoons of lukewarm milk, and leave at room temperature for 10 minutes to form a bubbling starter.
Heat the remaining milk gently in a saucepan and let the butter melt in it.
Place the flour in a bowl, add a pinch of salt, the remaining sugar, the egg, the milk and butter, and the yeast starter. Knead into a smooth dough, dust with flour, and leave to rise in a warm place for 1 hour, until the dough has at least doubled in volume.
Heat the oven to 320 °F (160 ºC). Grease a baking tray with some of the melted lard.
Roll out the dough on a floured surface into a roll measuring 1 inch (2,5 cm) in diameter and cut it into equal-sized pieces, which you then shape into balls in your hands.
Place the balls in a greased baking dish. Brush each one with melted butter on all sides. Place the baking dish in the preheated oven and bake for 20 minutes until golden brown.
Melt the butter in a saucepan, add the brown rum, and spread the hot mixture over the baked buns.