In a small bowl, toss together the cheddar and Parmesan. Sprinkle the cheese mixture into a large, heavy nonstick skillet. Cook over medium-high heat 2 to 3 minutes or until the cheeses are melted and bubbly. Tip skillet to allow excess oil to collect in one place. Remove excess oil with a spoon. Carefully lift the large crouton from the pan with a spatula and drain on paper towels. Cool and crumble.