Chef Bryant Ng uses a salted duck egg yolk in his sauce for grilled asparagus. Home cooks can get the same delicious effect with a creamy sauce made with hard-cooked egg yolk, cream, ginger, garlic and chiles.
In a medium saucepan, heat 1/2 tablespoon of the oil. Add the Thai chile, minced ginger and half of the garlic and cook over moderate heat until softened, about 2 minutes. Add the butter and swirl until melted. Add the egg yolk and whisk until blended. Add the cream, season with salt and pepper and simmer just until slightly thickened, about 2 minutes.
Light a grill or preheat a grill pan; oil the grates. Grill the asparagus, turning occasionally, until crisp-tender, about 5 minutes. Transfer the asparagus to a work surface and cut them into 2-inch lengths. In a large skillet, heat the remaining 1 tablespoon of oil. Add the Chinese sausage, sauerkraut, ginger matchsticks and the remaining garlic and cook over moderate heat, stirring occasionally, until lightly browned, about 2 minutes. Add the asparagus and scallion and stir-fry until heated through, about 1 minute. Remove from the heat and stir in half of the sauce. Transfer the asparagus to a platter and drizzle with the remaining sauce. Serve right away.