Roasted cauliflower & cashew soup with chaat masala croutons

Name: Roasted cauliflower & cashew soup with chaat masala croutons
Cuisine: Asian, Indian
Ingredients: 1 medium cauliflower; 4 tbsp olive oil; 2 tsp turmeric; 1 tsp table salt; 5 sprig/s sage; 1 tsp cumin seeds; 1 medium onion, chopped; 4 clove/s garlic, chopped; 2½ cm piece ginger, peeled and grated; 150g pack roasted cashew nuts; 2 Kallo Organic Vegetable Stock Cubes; 2 slice/s sourdough bread; 2 tbsp butter, plus extra to serve (optional); 2 tsp chaat masala (or as a spicier option, 2 tsp gunpowder spice blend with a with a squirt of lemon juice)