Preheat oven to 425°F (220°C). Toss halved Brussels sprouts with 1 tbsp neutral oil, 1/4 tsp sea salt and a grind of black pepper; spread in a single layer on a rimmed baking sheet. Roast 15–18 minutes, turning halfway, until deeply golden at the cut edges and tender — high heat caramelizes the sugars and builds savory roast flavor that stands up to the tamarind glaze.

While the sprouts roast, pat the pork slices dry with paper towels and season lightly with salt and pepper. Dry surface = better sear. Keep slices relatively even; if some are thicker, flatten gently with the palm to ensure even cooking.

Make the tamarind glaze: in a small bowl whisk together tamarind paste, soy sauce, honey, rice vinegar, grated ginger, minced garlic and 3 tsp toasted sesame oil. Taste for balance — tamarind is bright and tart, so you want a clear sweet‑sour counterpoint. If you like a glossier, clingier sauce, whisk the 1 tsp cornstarch into 1 tbsp cold water and set aside.

Bring a large pot of salted water to a rolling boil. Add fresh udon and cook 1–2 minutes until just tender (follow package instructions) — fresh udon cooks fast; overcooking makes it gummy. Drain, rinse briefly under warm water to separate strands, toss with 1 tsp neutral oil to keep from sticking and set aside.

Heat a large, heavy skillet or wok over medium‑high to high heat until shimmering. Add 2 tbsp neutral oil and swirl to coat. Add the pork slices in a single layer (work in batches if needed). Sear quickly — 1–2 minutes per side for thin slices — to get a golden crust without overcooking. High heat promotes Maillard browning, which adds savory depth to the finished dish. Transfer seared pork to a plate and tent loosely with foil to rest.

Reduce heat to medium‑high, add remaining 1 tbsp neutral oil to the pan and add carrot ribbons. Stir‑fry 1–2 minutes until they just begin to soften — you want them bright and slightly crunchy to add texture contrast. Add roasted Brussels sprouts (hot from the oven) and toss to combine; their caramelized edges will provide savory bursts among the noodles.

Push vegetables to the side of the pan, raise heat to high and pour the tamarind glaze into the cleared center; let it come to a simmer so flavors meld and alcohol/volatile aromatics evaporate. If using the cornstarch slurry, whisk it into the simmering glaze — the short cook will activate the starch and create a glossy coating that clings to noodles and pork. Simmering concentrates flavor and slightly thickens the sauce so it coats ingredients, not puddles.

Return pork to the pan along with the cooked udon. Add remaining 1 tsp toasted sesame oil and toss vigorously with tongs or two spatulas to combine — the hot pan and fast tossing heat the noodles through and marry the glaze to everything evenly. Taste and adjust seasoning with salt, pepper or a squeeze of lime if it needs an extra bright pop.

Finish off‑heat by folding in scallions and most of the cilantro (reserve some for garnish). Transfer to a warmed platter or individual bowls. Sprinkle with crushed peanuts or sesame seeds, additional cilantro, and serve with lime wedges for squeezing — immediate acid lifts the tamarind and brightens the whole plate.

Serve hot. Encourage diners to squeeze lime and add extra peanuts or sesame seeds to taste. Leftovers keep well refrigerated for 2 days; gently reheat in a skillet with a splash of water to loosen the noodles.