Grill your bread for a few minutes until crispy and golden. If you want some more garlic flavor you can cut a garlic clove in half and rub the open side over the warm sandwich. You'll be surprised how much flavor it gives.
Cut your tomatoes in quarters and season with pepper and salt. Sprinkle some olive oil over them and some apple vinegar.
Spread your crostini with the Boursin and top with the tomatoes. Sprinkle some balsamico over the tomatoes and eat straight away