Preheat the oven to 350 degrees F.
Cut the baguette in half lengthwise and place, cut sides up, on a baking sheet.
In a small bowl, mash the garlic with the oil and 3 tablespoons of the Parmesan. Spread the mixture evenly over both sides of the bread. Sprinkle each half with 1 1/2 teaspoons of the remaining cheese. Add a light sprinkle of Italian seasoning if using.
Bake on upper rack of the oven for 10 minutes or until the topping is golden. If the bread is hot throughout and you would like the top to brown a bit more, place under the broiler for a minute or so, watching very carefully to prevent burning.