In a blender, blend basil with olive oil. Strain through a coffee filter or cheese cloth. Season with salt and pepper.
Rub inside bread with roasted garlic. Layer bread with mozzarella and tomato. Drizzle with basil oil.
Heat large cast iron pan over medium high heat until very hot. Butter outside of sandwiches on both sides. Place 3 sandwiches at a time in pan and cover with another cast iron pan. Cook until brown. Turn over and brown other side. Repeat with remaining sandwiches.