Cauliflower soup with mustard and Gruyère croûtons – Gourmet Traveller

Ingredients

• 50 ml olive oil, plus extra to serve
• 50 gm butter, coarsely chopped
• 1 onion, finely chopped
• 2 garlic cloves, thinly sliced
• 1 large Desiree potato, finely chopped
• 1 kg cauliflower, trimmed into small florets
• 1.75 litres (7 cups) chicken stock
• 100 gm grated Gruyère
• 250 ml (1 cup) milk
• Mustard and Gruyère croûtons
• 30 gm butter, melted
• 30 ml olive oil
• 2 tbsp Dijon mustard
• 2 tbsp grated Gruyère
• 100 gm day-old sourdough, coarsely torn