Prepare your slow cooker: Grease the inside of your slow cooker insert with a little butter or oil to prevent sticking. This step is quick and saves you from scrubbing later.

Add the base ingredients: Place the diced potatoes, chopped onion, minced garlic, chicken stock, butter, salt, pepper, dried thyme, and bay leaf into the slow cooker. Give everything a good stir. The liquid should just cover the potatoes — if not, add a splash more stock.

Cook on low: Set the slow cooker to low and cook for 6–8 hours. You'll know it's ready when the potatoes are fork-tender and the soup looks slightly thickened. The smell of garlic and herbs will fill your kitchen.

Remove the bay leaf: Once cooked, fish out the bay leaf and discard it. It has done its job infusing flavour, and you don't want anyone biting into it.

Blend until creamy: Using an immersion blender, blend the soup directly in the slow cooker until it's smooth and velvety. If you prefer a chunkier texture, only blend half. The colour should turn from a pale broth to a rich, creamy white.

Add the cream and cheeses: Stir in the double cream, grated cheddar, and Parmesan. Let the soup sit on the 'keep warm' setting for 5 minutes. Stir again until the cheese is fully melted and the soup looks glossy and thick.

Taste and adjust: Give it a final taste. You might want a pinch more salt or pepper. The texture should be thick enough to coat the back of a spoon, yet still pourable.

Serve and garnish: Ladle the soup into bowls and top with sliced spring onions, extra grated cheddar, and a dollop of sour cream if you like. The contrast of the hot, creamy soup and the cool, fresh toppings is absolutely lovely.