Place the bacon under a preheated hot grill and cook for 1-2 minutes or until crispy.
Place the mayonnaise, garlic, lemon juice, chives and chicken in a bowl and mix well to combine. Spread both sides of the bread with butter. Divide cheese and chicken mixture between 4 slices of bread and sandwich with another slice of bread.
Heat a large non-stick frying pan over low heat. Cook he sandwiches, in batches, for 3-4 minutes each side or until golden and the cheese is melted.