Preheat the oven to 325 degrees F.
In a mixing bowl, toss the garlic pieces with the olive oil to coat evenly. Spread the garlic pieces evenly on the bottom of a small baking pan and roast until their edges begin to brown, 25 to 30 minutes.
Remove the pan and with a spoon or spatula, scrape up and turn the garlic; then return the pan to the oven and roast until the garlic is uniformly golden brown, about 15 minutes more. Set aside to cool completely.
Put the roasted garlic pieces and 2 tablespoons of the water in a food processor fitted with the steel blade. Process, scraping the bowl down occasionally, until the garlic is pureed to a paste with the consistency of smooth peanut butter. If necessary, add the remaining water. Transfer to a bowl, cover and refrigerate until ready to use.
Yield: 1/2 cup