Meanwhile, start cooking the pasta according to the package instructions.
300 g pasta shells
Pour in the milk and add the pureed pumpkin. Whisk the roux together, so there are no lumps and the sauce begins to thicken and turn smooth and creamy.
250 ml milk, 300 g 1 cup pureed pumpkin
Add in about ¾'s of the cheddar cheese and gouda cheese.
80 g gouda, 80 g cheddar cheese
Then, stir in the cooked pasta and the starchy pasta water, making sure all of the pasta shells are coated.
120 ml starchy pasta water
Top the pasta with the remaining cheese, then grill for 5 minutes or until the cheese has melted and turned golden and bubbly.
Your pumpkin mac and cheese will last in the refrigerator for around 4-5 days. You could either cover the roasting dish with foil or cling film and store it in the fridge, or you could transfer any leftover pumpkin mac and cheese to an airtight container.