Bring a large stockpot filled with 5 cups of water to a boil. Once boiling, add the pasta and cook 8-10 minutes, or until al dente. If the pasta start looking dry, add another 1/4 cup of water, if needed.While the pasta cooks, melt 2 tablespoons of butter over medium heat in a skillet. Once melted, add the crushed cornflakes and garlic powder. Toss the cornflakes in the melted butter and toast until they’re golden and fragrant. Remove from heat.When pasta is ready, DO NOT DRAIN. The remaining pasta water will help thicken the cheese sauce. Reduce the heat to low and then, to the pasta, add the remaining 4 tablespoons of butter and the cubed cream cheese. Stir until melted and creamy. Then add the milk, salt and pepper and mix until incorporated.Remove the pot from the heat and gradually stir in the gruyere, fontina and cheddar cheese a half cup at a time. Mix until each addition is melted and a smooth before adding the next. If the sauce is thicker than your care for, add a few tablespoons of milk to thin the sauce to the desired consistency.Finally, top with the toasted garlic cornflakes and chopped fresh parsley. Drizzle lightly with truffle oil, if desired. Serve immediately.