Silky leek and potato soup with mustard croutons and coriander garnish

Ingredients

• 2 tablespoons unsalted butter
• 4 large leeks, white and tender green parts only, thinly sliced
• 1 white potato, peeled and cut into chunks
• 3 cups chicken stock
• 2 cups Anchor milk powder (6 full tablespoons of Anchor powder mixed in 2 glasses of water)
• Salt and freshly ground pepper
• Fresh coriander leaves for garnish
• Olive oil
• 1 or 2 day old bread of your choice
• 1 tbsp of Dijon mustard cooking spray