To an oven-safe, deep frying pan, add olive oil and the brussels into the pan and heat over a medium/high heat. Season with salt and pepper and fry for 3 minutes.
Meanwhile, add your pasta to salted boiling water. Timer set to 2 minutes less than the packet states.
Once the brussels have taken on some colour, reduce the heat to medium/low and add the onions into the pan. Fry for 5 more minutes, adding the garlic for the final minute of fry time.
Next, add the Hellmann’s mayonnaise, 100g of cheddar, dijon mustard into the pan. Slowly stir 400ml of pasta water.
Transfer the undercooked pasta into the pan & stir to combine, continuing to heat over medium/low. The pasta water should thicken into a cheesy glossy sauce.
Top with 60g of cheddar and pop under the grill for 6-8 minutes, or until the cheese is melted and golden. Top with fresh parsley/basil and season with lots of black pepper. Enjoy!