Stir-fried beef with Chinese greens from Winter Food by Jill Norman

Ingredients

• 800 g lean beef, such as sirloin or rump
• 80 ml soy sauce
• 60 ml rice or wine vinegar
• 3 cm ginger, peeled and shredded
• 2 cloves garlic, finely sliced
• 2 red chillies, seeded and finely sliced
• 4 spring onions, finely sliced
• 2 teaspoons sugar
• 4 tablespoons sunflower oil
• 500 g mustard greens, trimmed and shredded
• peel from 1 well-scrubbed tangerine, cut into long strips
• 2 teaspoons sesame oil