1. Melt the butter in a large saucepan over medium heat. Add the onion, garlic and cumin, and cook, stirring, until the onion softens.
2. Add potato and cauliflower, and stir to coat. Add stock and bring to the boil. Reduce heat to medium and simmer, covered, for 20 minutes or until potato is tender. Remove from the heat and allow to cool slightly.
3. Use a stick blender to blend mixture until smooth.
Stir through the cream and cumin. Season the adult portions and serve with crispy croutons.