1On 1 side of each of 4 bread slices, spread 1 tablespoon preserves. Layer with chicken and cheese. On 1 side of each of 4 remaining bread slices, spread 2 teaspoons mustard. Place slices, mustard side down, on cheese.
2On griddle or 12-inch nonstick skillet, heat 1 tablespoon of the butter over medium heat. Place sandwiches in skillet. Spread tops of bread with remaining 2 tablespoons butter. Cook 6 minutes, turning once, until cheese is melted and bread is golden brown.