Preheat the oven to 200°C. For the cheese sauce, first make some infused milk by lightly simmering 2 cups of milk with 2 garlic cloves, some fresh thyme and 1 teaspoon of nutmeg, until fragrant. Strain the milk. In a saucepan, combine 6 T butter with 6 T flour and cook for a minute or two. Gradually add the infused milk and stir until it’s thick and smooth. Season to taste, then add 300 g grated mature Gouda. Fry 250 g portabellini mushrooms in 1 T ghee, olive oil or butter, until soft and tender. Place 500 g cooked pasta in an ovenproof dish. Add the mushrooms and the cheese sauce and stir through. Sprinkle with more grated Gouda, drizzle with truffle-infused olive oil and bake for 20-25 minutes in the oven until golden and bubbling.