Chickpea and Potato Biryani

Name: Chickpea and Potato Biryani
Ingredients: 3 tablespoons oil; 1 medium sized onion, thinly sliced; 1 tablespoon freshly grated ginger; 1 medium sized tomato, diced; 1 cup of dark brown cooked chickpeas (kala chana); 1 medium sized white potato, peeled and quartered; 1 medium sized purple potato, peeled and quartered; 1 teaspoon salt; 1 and 1/2 teaspoons garam masala powder; 1 teaspoon crushed whole black peppercorns; 1 cup of basmati rice, soaked for 30 minutes and drained thoroughly; 3 whole black cardamoms; 2 bay leaves; 1 teaspoon saffron strands; 1 and 1/2 tablespoons finely chopped mint; 2 to 3 tablespoons fresh lime juice