Poach 1 chicken breast in a small sauté or saucepan in enough water to cover by an inch. (Bring to boil, then reduce and barely simmer, partially covered, 10 minutes. Remove from heat and let sit in water 10 minutes.) When cool enough to handle, cut into chunks and pulse in processor until finely chopped. This should yield about 1/2 cup.
In a medium-size bowl, combine chicken with 1/3 cup or so diced apple, 1/4 cup mayo, 1 teaspoon lemon juice (optional), and salt and pepper to taste. (This is basic version; can add any desired seasonings.) Stir until thoroughly combined.