Complete the following statement based on the text.

Mackerel Tuna Curry

Ingredients:

• 1 mackerel tuna, cut into 6 pieces
• 2 tbsp lime juice
•  tsp pepper powder
• 3 tbsp cooking oil
• 2 sticks of lemongrass, bruised
• 2 lime leaves, remove the tips
• 2 cm ginger, crushed
• 400 ml coconut milk from 1 grated coconut
• 3 stalks of basil leaves, take the leaves
• salt
• 6 shallots
• 4 cloves of garlic
• 3 cm of turmeric, peeled and grind
• 6 red chillies

Directions:

1. Smear the fish with lime juice,  teaspoon of salt, and pepper. Let it for 15 minutes to marinate.
2. Grill the fish until cooked.
3. Make the seasoning for the curry. Crush shallots, garlic, turmeric, and chillies.
4. Heat the oil. Stir-fry the seasoning until fragrant. Add lemongrass, lime leaves, and ginger, cook until fragrant.
5. Add tuna and stir slowly, so the fish will not break. Add the coconut milk and salt, cook until boiling and thick.
6. Add the basil leaves and mix well.
7. Pour on the serving plate and serve it as the side dish.

(Adopted from: Siti Fatimah, Menu Rumahan Favorit, Jakarta, Kala Media, 2011.)

The cooking oil is used to ____.