Red lentil and butternut squash soup

Ingredients

• 2 tbsp olive oil
• 2 fat garlic cloves, finely chopped (optional)
• 7.5cm/3 inch piece root ginger, peeled and finely grated
• ½ tsp red chilli flakes (optional)
• 300g/10½oz red lentils
• 1.2 litres/2 pints hot vegetable stock
• 300g/10½oz butternut squash, cut into 1cm/½-inch cubes
• salt
• freshly ground black pepper