Finely dice tomatoes and place in a bowl.
Cut basil either into thin ribbons (chiffonade) or small dice. Add to tomatoes.
To the bowl, add the balsamic, 1/2 Tbsp olive oil. salt, and 1 clove minced garlic. Stir to incorporate. Cover and chill for at least one hour.
When ready to serve, slice the baguette into 1/2 inch coins on the bias (at an angle). Lay them out on a cookie sheet and lightly drizzle with olive oil. Bake them at 300F. After 5 minutes, flip the crostini. Bake an additional 5 minutes, or until they just start to turn brown around the edges, and remove from the oven.
Let the bread cool slightly. Unpeel the whole garlic cloves and rub them against the toasted bread, flavoring each piece. Serve with the chilled tomato mixture.