Charred Eggplant and Tomato Curry with Potatoes and Peas

Name: Charred Eggplant and Tomato Curry with Potatoes and Peas
Ingredients: 1 large long eggplant; 1/4 cup vegetable oil or ghee; 1 medium onion, finely minced; Sea salt; 3 tablespoons finely grated ginger; 4 garlic cloves, finely grated; 1 teaspoon garam masala powder; 1 teaspoon ground turmeric; 1 teaspoon ground coriander; 1 teaspoon ground cumin; 1/4 to 1 teaspoon cayenne pepper (to taste); Seeds from 4 cardamom pods; One 15-ounce can crushed tomatoes; 2 medium potatoes, cut into cubes; 1 cup peas; 1/4 cup heavy cream (optional)