Preheat and prep: Preheat your oven to 425°F (220°C). This high roasting temperature encourages browning on the potatoes and gives the pork a quick finish in the oven without drying. Line a rimmed baking sheet with foil or parchment for easy cleanup.

Prep the potatoes: Place 12 small halved baby potatoes in a large bowl. Toss with 2 tablespoons olive oil, 2 cloves minced garlic, 1 teaspoon kosher salt and 1/2 teaspoon black pepper. Spread cut-side down on the prepared baking sheet. Roasting cut-side down encourages contact browning for a deep golden crust.

Begin roasting potatoes: Slide the potatoes into the preheated oven and roast for 20 minutes while you prepare the pork. They will be par-cooked and will finish while the pork rests, ensuring everything finishes at the right doneness.

Trim and season the pork: Pat the 720 g pork tenderloin dry with paper towels (dry surfaces brown better). Trim any silver skin and, if the tenderloin is uneven, tie it loosely into a uniform cylinder with kitchen twine to ensure even cooking. Season generously all over with salt and pepper.

Sear the pork for a browned crust: Heat a large, ovenproof skillet (cast iron preferred) over medium-high heat until shimmering. Add 1 tablespoon olive oil and swirl. Sear the pork 2–3 minutes per side — including the ends — until a deep golden-brown crust forms. Browning (the Maillard reaction) adds concentrated savory flavor and color.

Deglaze and make the apple-cider glaze: Remove the pork briefly to a plate. Lower heat to medium, add the 1 cup apple cider to the hot pan to deglaze, scraping up browned bits (those are flavor). Stir in 4 teaspoons Dijon mustard and bring the cider to a simmer. Reduce gently until syrupy and reduced to about 1/3 cup (about 6–8 minutes). Reducing concentrates the cider’s sweetness and allows the mustard to emulsify into a glossy glaze.

Finish glaze and roast pork: Whisk a tablespoon of unsalted butter into the reduced glaze off the heat to round and thicken it; this gives the sauce a silky sheen. Return the pork to the pan and spoon some glaze over it. Transfer the skillet to the oven alongside the par-roasted potatoes and roast for 10–12 minutes (or until an instant-read thermometer inserted into the thickest part reads 145°F / 63°C). The oven time will gently finish the pork without overcooking.

Roast the asparagus: While the pork roasts, toss 4 cups asparagus spears with the remaining 1 tablespoon olive oil, 1 clove minced garlic, a pinch of salt and pepper. Spread on a second baking sheet or a cleared spot on the first sheet. Roast 8–10 minutes until bright green and just tender — roasting keeps asparagus crisp-tender with some caramelized tips.

Rest pork and finish potatoes: When the pork reaches 145°F, remove the skillet and transfer the tenderloin to a cutting board. Tent loosely with foil and rest 8–10 minutes (resting lets juices redistribute; slicing immediately will lose more juice). While the pork rests, return the potatoes to the oven if needed and roast until golden and fork-tender, 5–8 more minutes. Toss potatoes with the remaining minced garlic and 4 tablespoons chopped parsley after roasting so the herb stays bright.

Slice and glaze: Slice the rested pork into 1/2-inch medallions. Rewarm the reduced glaze if it has thickened; spoon or brush it over the sliced pork so every bite is glossy and flavorful. Taste a potato and the asparagus to adjust salt and pepper just before plating.

Plate and garnish: On each plate, arrange a bed of garlic‑parsley potatoes, a neat bundle of roasted asparagus, and 4–5 slices of pork. Spoon any extra glaze over the pork and scatter the remaining chopped parsley for color and freshness. Serve immediately.