Heat the lard in a large Dutch oven or heavy casserole over medium-high heat. Season the meat with 2 teaspoons of the salt and the black pepper. Once the lard has melted, add the meat, brown on all sides, stirring and flipping as it does, for about 10 to 12 minutes.
In the jar of a blender, pour 1 ½ cups of the milk and add the garlic, onion and remaining 2 teaspoons of salt. Puree until smooth. Pour over the meat and let it come to a simmer, then reduce heat to medium-low, drop in the bay leaves, and cover. Cook covered for 1 hour and 15 minutes, flipping the chunks of meat a couple times in between.
In a small bowl, combine the remaining ½ cup milk with the sugar. Pour over the carnitas, stir, and let them continue to cook, uncovered, for another 4 to 5 minutes. Turn off the heat.
With a slotted spoon, remove the meat and place in a bowl. Shred with a couple forks, add a couple tablespoons of the seasoned fat remaining in the casserole and toss.