In a mini processor, puree the onion and garlic. In a medium saucepan, heat the oil. Add the puree and cook over moderately high heat, stirring, for 1 minute. Add the rice and cook, stirring, for 1 minute. Add the water and salt, stir well and bring to a boil. Add the parsley sprigs and jalapeño slices, cover and cook over low heat for 25 minutes.