Combine egg yolk, soy sauce, rice wine, cornstarch, salt, and Sichuan peppercorns in a bowl to make the marinade. Add pork; marinate for at least 30 minutes.
Mix vinegar, water, sugar, tomato paste, soy sauce, and cornstarch together to make the seasoning sauce.
Heat oil in a deep saucepan over medium-high heat. Roll the marinated pork in cornstarch until each piece is well covered. Deep-fry pork for 2 minutes. Remove and drain on paper towels.
Heat 1 tablespoon oil in a small saucepan over medium heat. Stir-fry green peppers and scallions for 30 seconds. Add lychees and pour in the seasoning sauce. Stir well until sauce thickens. Leave over very low heat.
Reheat the deep-frying oil. Re-fry pork until crisp, about 30 seconds. Drain and place on a warm plate. Pour the seasoning sauce on top. Sprinkle with sesame oil and serve at once.