Preheat panini press according to manufacturer's instructions.
Slice bread into 10 (1") pieces; slice each piece in half. Brush crust sides of each piece of bread with olive oil. Turn bottoms of bread, oiled side down. Place chocolate evenly on bottom pieces of bread; cover with tops of bread, oiled side up.
Place 5 sandwiches in panini press; cook 1 minute or just until chocolate begins to melt and bread is toasted. Repeat procedure with remaining sandwiches. Serve hot.