In a stand mixer, combine the 87 g sourdough starter, 355 g water, and 536 g bread flour, mixing on low-medium until no dry flour remains and a rough dough forms. Cover and let the dough rest for about one hour.
After resting, add the 12 g sea salt little by little and mix on low-medium for about 5 minutes, allowing the dough to develop strength and become smoother.
Begin incorporating the 4 tbsp pork lard (68 g) gradually, adding a little at a time and letting it fully absorb before adding more, until it is completely incorporated into the dough. Once all the lard is incorporated, knead on low-medium for 5 minutes.
Add the 1 tbsp black pepper, meats (100 g prosciutto (3.4 oz.), 30 g pepperoni (1 oz.), 42 g salami (1.5 oz.),), and 80 g mild provolone (2.8 oz.), then continue mixing until the dough is smooth, elastic, and the fillings are evenly distributed.
Cover and transfer the dough to a warm place and let it rise until doubled in size.
Once risen, divide the dough into four equal pieces, about 300 grams each. Flatten each piece into a rectangle, then roll it into a loaf shape.
Place the shaped loaves onto a parchment-lined and floured baking tray, cover with a towel, and refrigerate overnight.
The next day, remove the loaves from the fridge and let them come to room temperature for about one hour while you preheat the oven to 400°F.
Brush the loaves with melted lard, score the tops, and place a few ice cubes under the parchment on the tray to create steam.
Bake for about 45 minutes, or until the loaves are golden brown.