How to Make It
In a large nonstick frying pan, heat the oil over moderately low heat. Add the onion and sauté, stirring occasionally, until it begins to soften, about 3 minutes. Add the garlic, ginger, and jalapeño and cook, stirring, for 1 minute longer. Stir in the curry powder and then the chicken broth. Bring the liquid to a simmer. Stir in the cubed chicken, cover the pan, and remove it from the heat. Let the chicken steam in the hot broth until almost done, about 5 minutes. Add the apple, tomatoes, coconut milk, salt, and the cilantro, if using. Simmer gently until the sauce thickens slightly, about 3 minutes.
In a large pot of boiling, salted water, cook the vermicelli until just done, about 9 minutes. Drain the pasta and toss with the curry sauce.