Heat oil in a wide skillet over medium-high. Add pork in a single layer and let it sit 2–3 minutes until the bottom caramelizes and darkens.
Break apart and continue cooking until most pieces have crispy, caramelized edges, 3–4 more minutes. Remove pork and set aside.
Build the Sauce
In the same pan over medium heat, add garlic and cook 30 seconds until fragrant. Add chili crisp, soy sauce, oyster sauce and sugar.
Add stock and bring to a simmer.
Cook the Noodles
Add udon directly to the sauce. Toss gently to loosen. Udon is fragile before it heats through, don't force it. Let the noodles absorb the sauce 2–3 minutes until thick, dark, and clingy.
Finish and Plate
Return pork to the pan, toss quickly. Finish with scallions, sesame seeds, and a heavy chili crisp drizzle.