Preheat oven to 325°.
Melt butter in a small nonstick skillet over medium heat. Add onion and garlic, and sauté 4 minutes. Add chicken livers; cook 2 minutes or until livers lose their pink color. Add port, and cook 3 minutes or until most of liquid evaporates. Cool.
Place chicken liver mixture, salt, and next 5 ingredients (salt through allspice) in a food processor or blender; process until smooth, scraping sides of bowl occasionally. Add the sour cream, chicken breast, and cream cheese; process until smooth, scraping sides of bowl occasionally. Spread chicken mixture into an 8 x 4-inch loaf pan coated with cooking spray.
Bake at 325° for 1 hour or until a thermometer registers 170°. Cool; cover and chill 8 hours. Serve at room temperature.