Preheat oven to 200℃ (180°C fan forced). Spray a 20 x 30cm baking dish with non-stick cooking spray.
Place potato into a large saucepan and cover with cold water. Bring to the boil over high heat, then reduce to medium-low and simmer for 5 minutes. Drain well.
Heat a frying pan over medium heat and cook the diced bacon until golden and crispy. Remove a small handful of the bacon and set aside for topping.
Add the diced onion to the pan with the remaining bacon and cook until soft. Stir in the garlic and cook for another minute.
In a large bowl whisk together the thickened cream, cream of chicken soup mix, curry powder, Dijon mustard and milk or water until smooth. Season with cracked black pepper.
Add the drained potatoes and the bacon and onion mixture to the bowl. Gently stir until everything is well coated in the creamy sauce.
Transfer the mixture to a baking dish and spread evenly. Bake for 25-30 minutes.
Remove and sprinkle top with grated cheese. Return to the oven and continue baking for a further 15-20 minutes or until potatoes are tender and the cheese is golden and bubbling.
Remove from oven and allow to rest for 5-10 minutes. Scatter the reserved crispy bacon and sliced spring onions over the top before serving.