Grease a baking dish with oil. Cook the pasta in lightly salted boiling water according to package instructions. Drain and return to the warm pot.
In a large saucepan, melt butter over medium heat, add onion and cook for 2-3 minutes.
Now, stir in flour, salt, and black pepper, and add milk (whisking constantly) until thickened. Then remove from heat.
Add mozzarella cheese, cheddar cheese, Gouda cheese, and half of the Parmesan cheese, whisking until cheeses are melted and the sauce is smooth.
Now, pour the cheese sauce over the cooked pasta; stir to coat. Transfer the mixture to the baking dish.
In a microwave-safe bowl, melt the 1 teaspoon butter, then stir in panko and the remaining Parmesan cheese and sprinkle the mixture over the pasta.
Bake for 5-10 minutes or until the top is browned. Garnish with parsley and serve.
Notes
When taking the saucepan off the heat to add the cheeses, go slow with the process. Add the one cheese, and let it dissolve into the sauce before adding the next. It's also a good idea to have them cut in chunks or grated for a faster liquefying process.
When you're making the béchamel sauce which is the name of the sauce, right before you add the cheeses in, make sure the milk doesn't come to a boil.
Variations
Add a spoonful of cream to the béchamel sauce for a richer consistency and taste.
You can also add a bit of garlic to your mac and cheese for flavour.
We've kept this recipe quite subtle. Nevertheless, feel free to spice it with herbs or condiments of your choice. It can be mustard powder, chilli powder, nutmeg or miso paste for all you like.
You can also substitute the cheeses for any cheese of your choice. It's a good idea to keep the cheddar for that classic flavour, but you can consider adding blue, gruyere cheese etc.