Preheat the oven to 180 °C and grease a 40 cm casserole baking dish.

Shred potatoes on the large side of a box grater. Place into a colander, rinse thoroughly and squeeze out any excess water. Place the potatoes into a large mixing bowl.

Heat one tablespoon of the Spreado in a medium-sized frying pan over medium heat. Add the onions and sauté until browned and softened. Add the green pepper and spring onion and sauté for a further 4 minutes. Set aside.

Melt the remaining Spreado in a medium-sized saucepan over medium heat. Sprinkle in the flour and stir well. Stir for a few seconds, and then slowly start pouring in chicken stock while continuing to stir. Once it is incorporated, add the milk and continue to stir. Lower the heat to medium-low. Allow the mixture to heat through and start to thicken, stirring often. Add 100 g of the cheese, in batches, until melted. Season with salt and pepper. Whisk in the sour cream, the parsley and the cooked onion mix and combine. Remove from the heat.

Mix the potatoes and cheese sauce in a large bowl and spread the mixture evenly in the greased casserole dish.

Sprinkle the rest of the cheese on top and bake for  40-45 minutes, until the cheese is golden and bubbly and the potatoes are cooked through.

Remove from oven, allow to cool slightly, garnish with chives and serve.