Choliya / green chana curry

Ingredients

• 1(310 gm) packet frozen Punjabi choliya (green chana)
• 1 onion (heaped 1/2 cup when ground)
• 1/2 cup crushed tomatoes
• 1 tsp turmeric
• 1.5 tsp red chilly powder
• 1.5 tbsp ginger and garlic paste
• 1 potato, diced
• 1/4 cup chopped cilantro
• 2 black cardamom,smashed (once by rolling pin)
• 3 tbsp oil
• salt as per taste
• 2 cups water to cook in pressure cooker