Slice the liver and kidneys thinly, then cut into thin strips about 1 ½ inch by 1 inch. Put the liver strips in one bowl and the kidney strips in another.
Combine the soy sauce, wine or sherry and sugar, then pour equal quantities of the mixture over the liver and kidneys, gently tossing the strips to coat them thoroughly. Set aside to marinate at room temperature for 3 hours, basting occasionally.
Fill a large saucepan one-third full with oil and heat until it reaches 185°C (360°F) in a deep-fat thermometer.
Carefully lower the liver strips into the oil and cook for 1 minute of until they are brown and crisp. Remove from the oil and drain on paper towels. Keep hot while you fry the kidney strips in the same way.
To make the dip, fry the pepper and salt in small frying-pan, stirring constantly. Remove from the heat and transfer the mixture to a small serving bowl.
Serve the liver and kidney strips at once, accompanied by the dip.