Cook rice according to package directions, omitting salt and fat.
Combine 1 tablespoon cornstarch, sherry, and pork, tossing well. Combine 1 tablespoon cornstarch, water, sugar, vinegar, soy sauce, and ketchup, stirring with a whisk.
Heat the peanut oil in a large nonstick skillet over medium-high heat. Add pork mixture; stir-fry 3 minutes. Add cashews, green onions, ginger, and garlic; stir-fry 1 minute. Add snow peas and pineapple; stir-fry 3 minutes or until snow peas are crisp-tender.
Add vinegar mixture to pan; bring to a boil. Cook 1 minute, stirring frequently. Serve the pork mixture over rice.