Pat the pork cubes dry with paper towels. In a bowl, combine 1 tablespoon of the kosher salt and the black pepper; sprinkle over the pork and toss to coat. Place the flour in a shallow bowl or plate and dredge the pork pieces, shaking off excess.

Brown the Pork

Heat vegetable oil and 1 tablespoon butter in a large Dutch oven or heavy-bottomed pot over medium-high heat until shimmering. In batches (do not overcrowd), brown the floured pork on all sides, about 3–4 minutes per batch. Transfer browned pieces to a plate and repeat until all pork is browned. Pour off any excess fat, leaving about 1 tablespoon in the pot.

Sweat the Mirepoix

Reduce heat to medium. Add the diced mirepoix (onion, carrot, celery) to the pot and a pinch of salt. Cook, stirring occasionally, until softened and beginning to color, about 6–8 minutes. Add the minced garlic and cook 30–45 seconds until fragrant.

Build the Sauce

Stir in the tomato paste and cook 1–2 minutes until it darkens slightly. Add the dried thyme and bay leaves. Pour in the Guinness to deglaze the pot, scraping up browned bits from the bottom. Let the stout reduce slightly for 2–3 minutes.

Simmer

Return the browned pork and any accumulated juices to the pot. Add the stock, Worcestershire sauce, and brown sugar. Bring to a gentle simmer, then reduce heat to low, cover partially, and simmer gently for 1 hour 15 minutes to 1 hour 30 minutes, until pork is very tender. Stir occasionally and skim foam or excess fat from the surface if needed.

Add Brussels Sprouts & Pearl Onions

About 20–25 minutes before the end of cooking, add the halved Brussels sprouts and pearl onions to the stew so they cook through but retain some texture. Adjust seasoning with remaining kosher salt (about 1/2 tablespoon) and more black pepper to taste. Continue simmering uncovered if you want a slightly thicker sauce; cover if you prefer more liquid.

Finish

When the pork is fork-tender and the sprouts are cooked, stir in chopped parsley and a 1 teaspoon splash of red wine vinegar if using to brighten the sauce. Remove bay leaves before serving. Taste and adjust seasoning.

Mashed Potatoes

Cook Potatoes

Place peeled, cut potatoes in a pot and cover with cold water by 1 inch. Add 1/2 teaspoon of the salt to the water. Bring to a boil over high heat, then reduce to a simmer and cook until potatoes are fork-tender, about 12–15 minutes.

Warm Dairy

While potatoes cook, warm the milk and cream (if using) with the butter in a small saucepan or microwave until butter melts and liquid is hot but not boiling.

Mash & Season

Drain potatoes well and return to the hot pot off the heat for a minute to dry. Mash with a potato masher or ricer until mostly smooth. Gradually add the warmed milk-butter mixture while mashing until you reach desired creaminess. Stir in remaining 1/2 teaspoon salt and 1/2 teaspoon black pepper; taste and adjust seasoning.

Roast/Finish Brussels Sprouts (optional for texture)

If you prefer roasted, caramelized Brussels sprouts instead of stewing them in the sauce: preheat oven to 425°F (220°C). Toss 1 lb halved sprouts with 1 tablespoon olive oil and a pinch of salt and pepper on a rimmed baking sheet. Roast 18–22 minutes, turning once, until deeply browned and tender. Add roasted sprouts to the stew in the final 5 minutes to mingle flavors, or serve on top of mashed potatoes with spoonfuls of stew.

Serve

Divide mashed potatoes among bowls or plates. Spoon a generous portion of pork stew with Brussels sprouts over the potatoes. Ladle some of the stout-rich sauce on top. Garnish with additional chopped parsley. Serve hot.