- STEP 1
Add the potatoes to a pan of boiling water and cook until tender.
- STEP 2
Drain then put back in the pot with a knob of butter and the ginger then mash until smooth. Keep warm.
- STEP 3
Heat a little oil in a wide pan and add the onions. Cook for about 5 minutes until softened. Move the onions to the edge of the pan and turn up the heat. Add the tuna and cook for 1 minute each side for rare, 2 for medium. Add the soy sauce to the pan and turn the tuna and onions to coat.
- STEP 4
Serve the tuna topped with the onions and the mash on the side.