Step 1: Cook the PastaStart by boiling a pot of salted water. Add the elbow macaroni and cook according to the package instructions until al dente. Drain and set aside.Step 2: Prepare the Cheese SauceIn a large saucepan over medium heat, melt the butter. Stir in the flour to form a roux. Cook for about 2 minutes, stirring constantly to prevent burning. Gradually add the milk, whisking constantly to avoid lumps. Cook until the sauce thickens, about 5 minutes.Step 3: Add the CheeseRemove the saucepan from the heat and add the grated cheddar cheese. Stir until the cheese melts completely. Season with salt and pepper to taste.Step 4: Combine the Pasta and SauceFold the cooked macaroni into the cheese sauce until well coated. Transfer to a greased baking dish.Step 5: Toppings and BakingSprinkle the top of the macaroni and cheese with grated Parmesan cheese and ground nutmeg. Then, drizzle with olive oil and scatter the diced bacon over the top.Bake the macaroni and cheese in a preheated oven at 180 degrees Celsiusfor 20-25 minutes, or until the top is golden and bubbly