Cover potatoes with water and bring to a boil, season with salt and cook to tender, 12-15 minutes. When potatoes are ready, drain and return to hot pot, mash with buttermilk to the desired consistency. Then, preheat the oven to 375°F.
Heat 1 tablespoon EVOO in medium skillet over medium heat and add 1/4 of the onions and half the garlic to pan and cook to soften, 5-6 minutes. Transfer the mixture to a bowl and cool. To cool onions add pork, a palmful of paprika, thyme, salt and pepper, mustard, egg and breadcrumbs. Mix to combine and form 4 loaves 2 inches thick, drizzle liberally with EVOO and arrange on parchment lined baking sheet and roast 35-40 minutes until firm and golden.