Prep the shrimp: Peel and devein the shrimp. Save the heads and shells for the stock.
Blanch the bok choy: Boil the bok choy briefly until just tender. Transfer to cold water, then drain.
Make the shrimp stock: Sauté the shrimp heads and shells until lightly browned, pressing on the heads to release more flavor. Season lightly, add water, and simmer. Strain and set aside.
Make the sauce: Combine the soy sauce, oyster sauce, and shrimp stock. In a separate bowl, mix the cornstarch and water to make a slurry.
Prepare the noodles: Pour hot water over the miki noodles and gently separate. Drain and set aside.
Sear the shrimp: Brown the shrimp quickly over high heat, just until lightly browned and starting to turn pink. Remove and set aside.
Sauté the aromatics: Cook the garlic and onion until softened.
Build the sauce: Pour in the sauce and bring to a boil. Stir in the slurry and cook until slightly thickened. Taste and adjust.
Add the noodles: Add the miki noodles and toss gently until coated and heated through.
Add the shrimp and vegetables: Add the shrimp and bok choy. Toss gently just until combined.Add some ground pepper, scallions, or celery leaves, if you like, Serve with lemon or calamansi on the side.