Pat the pork tenderloins dry with paper towels and season lightly with salt and cracked black pepper. Drying the surface removes excess moisture and helps the meat form a better sear (browning requires a dry surface).

Make the chipotle-citrus marinade: in a small bowl whisk together chipotle paste (4 tsp), 90 ml of the orange juice (reserve 30 ml for the pan sauce), 2 tbsp (2 of the 4 tbsp) olive oil, 2 crushed garlic cloves, and 2 tsp chopped rosemary. The oil carries fat-soluble flavor from the chipotle, the orange juice brightens and gently tenderizes, and garlic/rosemary add savory notes.

Brush or spoon the marinade evenly over the pork. Let rest at room temperature for 15–30 minutes (or refrigerate up to 2 hours). Don’t marinate for much longer than a few hours in citrus — the acid can start to “cook” and toughen the surface proteins if left too long.

Meanwhile, prepare the potatoes: place halved fingerlings in a medium pot, cover with cold water by 1 inch, add a generous pinch of salt and bring to a simmer. Parboil 8–10 minutes until just fork-tender but not falling apart. Parboiling jump-starts the cooking so the interior is creamy while the exterior roasts crisp.

Drain the potatoes and let them steam-dry in the colander for a minute; toss immediately with the remaining 2 tbsp olive oil, the remaining 2 tsp chopped rosemary, 2 crushed garlic cloves, and a pinch of salt and pepper. The hot potatoes will absorb the oil and aromatics, helping them brown beautifully in the pan.

Preheat your oven to 425°F (220°C). Heat a heavy, oven-safe skillet (cast iron preferred) over medium-high heat until smoking point for oil is nearly reached. A hot pan gives you a fast, even sear that builds the fond (browned bits) necessary for a flavorful pan sauce.

Sear the pork: add 1 tsp oil to the pan, then sear the pork tenderloins, presentation side down first, for 2–3 minutes until a deep golden-brown crust forms. Flip and sear the other side 2 minutes. Searing at high heat creates the Maillard reaction, concentrating flavor and locking juices into the meat’s surface.

Remove the pork to a plate. Add the potatoes to the hot pan in a single layer (don’t overcrowd—do in two batches if necessary). Let them brown undisturbed for 3–4 minutes, then toss and brown the other cut sides. Browning the cut faces gives texture and visual appeal.

Nestle the seared pork back into the pan among the potatoes. Transfer the skillet to the preheated oven and roast 10–15 minutes until an instant-read thermometer inserted into the thickest part of the pork reads 140°F (60°C) — the carryover heat will bring it to 145°F (63°C) as it rests. Roasting allows the pork to cook evenly without over-browning the exterior.

Remove the skillet from the oven and transfer the pork to a cutting board to rest 8–10 minutes; loosely tent with foil. Resting lets muscle fibers relax and reabsorb juices so slices stay moist.

While the pork rests, make the pan sauce: place the skillet back on medium heat (careful—handle will be hot). Add the reserved 30 ml orange juice to deglaze the pan, scraping up browned bits with a wooden spoon. Let the juice reduce slightly, then swirl in 1 tbsp butter off heat to gloss the sauce and round out the flavors. Taste and adjust seasoning. Reducing concentrates the citrus sweetness and integrating butter gives the sauce a silky finish.

Slice the pork into medallions (about 1/2" thick). Plate a bed of roasted fingerling potatoes, fan pork medallions on top, and spoon the chipotle-citrus pan sauce over and around the pork. Garnish with a few extra rosemary leaves and a crack of fresh black pepper. Serve immediately.