Heat oven to 400°F.
Place meat in a bowl and season with salt, white pepper and 5-spice powder. Add finely chopped scallions, grated ginger, grated garlic, breadcrumbs, egg yolk and sesame oil. Mix well and roll into small meatballs. Arrange on a baking sheet, drizzle with sesame oil and roast until brown and golden, 15-18 minutes.
Heat vegetable oil in a soup pot. Add mushrooms, sliced garlic, sliced ginger and chili pepper. Stir; add soy, water and stock, and simmer to flavor. Wilt in greens and cook to tender-crisp; combine with meatballs.
Cool and store, bring to room temp and reheat to a low boil. Add pasta and cook to al dente. Serve in shallow bowls garnished with sesame oil and thinly sliced scallions.