- Attach the sous-vide precision cooker to the side of a cooking container. Add enough water to come to the mid point between the minimum and maximum required. Set the temperature to 122°F (50°C). Set the cooking time to 15 minutes. Preheat the water while you prepare the fish.
- Using a mortar and pestle, coarsely grind the coriander seeds with the pepper flakes. Place the tuna steaks on a plate. Coat the tuna well with the coriander and red pepper flakes. Season with salt and pepper.
- Place the tuna steaks side by side in a sous vide bag or in a large freezer bag with a slider closing. Add the oil. Remove all the air from the bag. Submerge the bag in the preheated water (see note). Begin cooking (15 minutes).
- Preheat the grill, setting the burners to high. Oil the grate.
- Remove the bag from the water. Remove the tuna steaks from the bag. Grill the steaks for 1 minute on each side. Set aside on a plate. On a work surface, slice the tuna steaks.
- In a bowl, combine the fennel, mirin, oil and vinegar. Season with salt and pepper. Add the remaining ingredients and mix gently to combine.
- Divide the salad and tuna between two or four plates and serve immediately.
To remove the air from a freezer bag with a slider closing, hold the bag open at the top while slowly lowering it into the water. The pressure of the water will squeeze the air out of the bag. Just before the top of the bag reaches the water, zip it closed.
If using a freezer bag or one made of silicone, do not submerge the seal of the bag. Clip the top of the bag to the side of the cooking container ensuring the seal will not go underwater to prevent liquid from leaking into the bag.
It is important to ensure the food is fully submerged under water throughout cooking. If the food bag floats above water, use a large, heavy metal spoon, plate or any other heat resistant utensil to weigh the bag down to keep the food submerged.
To avoid risk of burn, carefully remove the bag from the water using tongs or oven mitts.