Preheat the oven to 375 degrees F. Place the garlic on a double-thick square of aluminum foil, drizzle with 1/2 teaspoon of the oil and fold up the foil to enclose the garlic securely. Place the garlic directly on the oven rack and bake until it is golden brown and meltingly soft, about 1 hour. Unwrap and set aside until cool enough to handle, about 5 minutes.
Combine the parsley, thyme and remaining 1 1/2 teaspoons olive oil in a small bowl. Remove the roasted garlic cloves from the white papery husks with the tip of a butter knife and place them in the bowl. Mash with a fork until smooth and spreadable. Spread the mixture evenly over the bread halves and sprinkle with the Parmesan and salt to taste. Place on a baking sheet and broil (about 6 inches from the heat source) until the top is just browned, about 2 minutes. Cut into 4 pieces and serve warm.
Halve the head of garlic horizontally, exposing a section of all the cloves. Use the bottom half for this recipe, and reserve top half for another use.