Pea and celery soup

Ingredients

• 1 teaspoon olive oil
• 1 onion, diced
• 1 large potato, peeled and diced
• 4 sticks celery, trimmed and sliced
• 700ml reduced-salt vegetable stock (made from 1 stock cube)
• 480g frozen petit pois
• 2 cloves garlic, finely diced
• 1 red chilli, deseeded and finely sliced or ¼–½ teaspoon crushed chillies (optional)
• Small handful fresh mint, leaves only (optional)
• Freshly ground black pepper, to taste