Preheat your oven to 200°C (400°F), or gas mark 6. Line a baking tray with parchment paper. Dissolve the stock cubes in 1 liter of boiling water, stirring until fully dissolved.
Cook the Leeks
Trim and clean the leeks, then slice them thinly. Drizzle 1 tablespoon of oil into a large pan over medium heat. Add the sliced leeks and sauté for about 10 minutes, or until they are softened and aromatic.
Add the Cauliflower and Simmer
Stir in the cauliflower florets to the pan with the leeks. Sprinkle in the curry powder, then pour in the stock. Bring the mixture just to a boil, then reduce the heat to low. Cover and simmer for 10 minutes, or until the cauliflower is tender. Use a wooden spoon to break up the cauliflower once it has softened and defrosted.
Prepare the Naan Croutons
Tear the naan bread into roughly 2cm pieces and spread them out on the prepared baking tray. Toss with 1 tablespoon of oil to coat. Bake for about 5 minutes, or until the pieces are golden and crispy.