Fish curry with Mustard

Name: Fish curry with Mustard
Ingredients: 2 Pounds firm-fleshed fish such as salmon, swordfish, mahi-mahi, cut into 4-inch pieces; 2 Teaspoons turmeric; salt to taste; 1 Teaspoon black mustard seed; 1 Teaspoon yellow mustard seed; 1 Teaspoon poppy seeds; 3 green chiles, 1 left whole, 1 halved lengthwise, and 1 seeded and slivered thinly; 1/4 Cup shredded unsweetened coconut; 1/4 Cup water; 1 onion, quartered; 1 piece (1 1/2 inches) fresh ginger, thinly sliced; 2 Tablespoons plain Greek Yogurt; 2 Tablespoons sunflower oil