Cook the macaroni in boiling water for about 10 minutes until tender but still firm. Drain well and set aside.
In a deep skillet, melt 6 tablespoons butter (5 tbsp unsalted and 1 tbsp truffle butter) over medium heat. Add the flour to make a roux and cook, stirring, to remove any lumps.
Pour in the milk and cook until the mixture is thick and smooth. Season mixture with salt and pepper. Add in the green garlicky herb oil. Off the heat, stir in both cheeses and stir until melted. Add the cooked macaroni and stir until macaroni is well coated.
Melt the remaining butter (1 tbsp unsalted and 1 tbsp truffle butter) and combine with the breadcrumbs, sprinkle on top of macaroni.
Transfer the mixture to a 3-quart baking dish. Preheat the over to 350 degrees. Bake for about 20-30 minutes until hot and bubbly.