Adjust rack to top position (top and middle positions for 4 servings) and preheat oven to 425 degrees. Wash and dry produce. Dice potatoes into ½-inch pieces. Trim and halve Brussels sprouts lengthwise.

Toss Brussels sprouts on one side of a baking sheet with a large drizzle of oil, salt, and pepper. (For 4 servings, spread Brussels sprouts out across entire sheet.)Roast on top rack for 12 minutes (you’ll add more to the sheet then).

Meanwhile, place potatoes in a medium pot with enough salted water to cover by 2 inches.Bring to a boil and cook until tender, 15-20 minutes. Reserve ½ cup potato cooking liquid, then drain. Return potatoes to pot; keep covered off heat until ready to mash in Step 6.

Pat pork* dry with paper towels and season with salt and pepper.Heat a drizzle of oil in a large pan over medium-high heat. Add pork and cook, turning occasionally, until browned, 4-8 minutes. Remove from heat.Once Brussels sprouts have roasted 12 minutes, remove sheet from oven. Transfer pork to opposite side. (For 4 servings, arrange pork on a second sheet; roast on middle rack.) Wipe out pan.Return sheet to top rack; roast until pork is cooked through, 10-12 minutes more. Transfer pork to a cutting board.

Meanwhile, halve orange. Pick parsley leaves from stems; roughly chop leaves.In a small bowl, whisk together brown sugar, mustard, stock concentrate, half the thyme, 2 TBSP water, and juice from half the orange (all the thyme, 4 TBSP water, and juice from whole orange for 4 servings). Heat pan used for pork over medium heat. Add orange mixture to hot pan and bring to a simmer. Cook, stirring constantly, until slightly reduced, 2-4 minutes.Remove from heat and stir in 1 TBSP butter (2 TBSP for 4) until melted. Taste and season with salt and pepper if desired.

Return pot with potatoes to medium-low heat. Add 2 TBSP butter (4 TBSP for 4 servings). Mash until smooth and creamy, adding splashes of reserved potato cooking liquid as needed. Taste and season with salt and pepper.Keep covered off heat until ready to serve.

Slice pork crosswise.Divide pork, Brussels sprouts, and mashed potatoes between plates. Spoon pan sauce over pork and mashed potatoes. Garnish everything with almonds and parsley. Serve.