In a small saucepan, gently heat the milk until it starts to bubble. Once it reaches this stage, remove it from the heat source. Next, slowly incorporate the sugar until it completely dissolves. Allow the mixture to cool down until it reaches a lukewarm temperature.
In a small bowl, combine warm water and yeast, allowing it to sit until a creamy texture forms, typically around 10 minutes.
In a large bowl, combine the milk mixture, yeast mixture, 3 cups of flour, and shortening. Beat the mixture until it becomes smooth. Then, mix in the salt and the remaining 3 cups of flour. Knead the mixture until a soft dough is formed. Grease a bowl, place the dough in it, cover it, and let it rise in a warm place until it doubles in volume, which usually takes about 1 hour.
Gently press the dough downward. Next, on a lightly floured surface, roll it out to a thickness of approximately half an inch. Use a biscuit cutter, a drinking glass, or an empty tuna can to create round shapes. Place the dough rounds on waxed paper sprinkled with cornmeal. Dust the tops with cornmeal as well, then cover them and allow them to rise for 30 minutes.
The greased griddle should be heated over medium heat.
The muffins should be cooked on a griddle until they achieve a light brown color, which usually takes around 10 minutes per side. Afterward, they can be split and toasted according to personal preference.