In a bowl dissolve cornstarch in soy sauce and stir in broth, zest and sugar. In a kettle of salted boiling water cook noodles until tender and drain well. While noodles are cooking, in a heavy skillet measuring about 10 inches across top heat 1 tablespoon of oil over moderately high heat until hot but not smoking. Stir-fry beef, patted dry and seasoned with salt and pepper, until browned, about 45 seconds, and transfer to bowl. Add the remaining 1/2 tablespoon oil to skillet and stir-fry garlic, gingerroot, and snow peas 30 seconds. Stir cornstarch mixture and add to snow peas, stirring. Simmer mixture until thickened and stir in beef with any juices accumulated in bowl and salt and pepper to taste. In a large bowl toss beef mixture with noodles. Serves 2. Gourmet April 1994