Bring a large pot of water to a boil. Add the pasta and salt. Cook according to the package directions until al dente. Drain, toss with a bit of olive oil and set aside.
Have your measured flour, butter, milk and cheese ready along with a small whisk. Recommended: Warm the milk in the microwave or a small saucepan.
Place a medium saucepan over medium heat. Add the butter and wait a few moments until melted. Then add the flour and garlic powder, whisking to incorporate and form a roux.
Let the roux bubble for about 30 seconds. Then dribble about a half cup of (warm) milk into the roux, whisking continuously. The sauce should be thickening steadily. Keep dribbling in more milk and whisk until it bubbles and thickens. Repeat until all the milk is used up. The sauce should be thick enough to coat a spoon, like a runny pancake batter. If not, then let cook longer but continue whisking to avoid lumps or sticking.
Remove the saucepan from the heat. Using a wooden spoon, mix in the grated cheese until completely smooth. Then mix in the truffle oil (it should lend a pleasant musky aroma to the cheese sauce).
Add the cooked pasta to the cheese sauce, stirring until completely coated.
Optional: For a golden topping, broil the mac and cheese. Preheat the broiler to maximum, setting the oven rack to the upper middle position (so the top of the pan will be 2 to 3 inches from the broiler). Turn the mac and cheese into a 13×9” pan. Sprinkle bread crumbs evenly on top. Place the pan in the oven and broil until bubbly and golden on top, about 3 to 5 minutes.
Serve warm and enjoy!