Cut chicken into bite-size chunks. Drain pineapple, reserving juice. Melt butter in a large skillet over medium heat; add chicken. Sauté with garlic until browned, about 5 to 10 minutes. While chicken is sautéing, start preparing rice.
To the chicken, add pineapple, sesame seeds, corn syrup, lemon juice, soy sauce, ginger and salt; mix well.
Dissolve cornstarch in reserved pineapple juice in a glass measuring cup. Add enough water to equal 2 cups. Pour over chicken mixture.
Simmer mixture uncovered over low heat, stirring occasionally, until sauce is thickened and chicken is cooked through, about 20 minutes. Serve over rice. Garnish with pineapple rings and parsley, if desired.
NOTE: Make ahead - Combine the ingredients in step 2 up to 8 hours ahead. Store in the refrigerator until ready to use.
VARIATION: For a tropical twist, use lime juice instead of lemon juice. Sprinkle with chopped peanuts and/or coconut.