Shrimp Balchao from How to Cook Indian by Sanjeev Kapoor

Ingredients

• 2 large onions, finely chopped
• ¾ cup (150 ml) vegetable oil
• 2 tablespoons sugar
• 2 large tomatoes, chopped
• 1 teaspoon black mustard seeds
• 2-inch (5-cm) cinnamon stick, broken
• 1 cup (200 ml) malt vinegar or cider vinegar
• 15 dried red chiles, stemmed and broken in half
• 10 to 12 whole cloves
• 10 cloves garlic
• 1 teaspoon cumin seeds
• 1 teaspoon table salt
• 2-inch (5-cm) piece fresh ginger, chopped
• 40 medium shrimp, shelled and deveined