Step 1

Preheat the oven to 220ºC. Prick the potatoes all over with a fork. Place the potatoes onto a plate and microwave on high (800 watts) for 10 minutes, until cooked through. Place the potatoes onto a baking tray, rub with a little oil and bake in the oven for 10 minutes.

Step 2

Wash and roughly slice the celery. Add the mayo, yoghurt, herbs, capers and celery to the chopper attachment of the Triblade Hand Blender, then blitz. Add the lemon zest and juice, tasting to see if it needs any extra seasoning. Drain the tuna and scoop it into a mixing bowl. Add the mayo and yoghurt mix, season with salt and pepper then stir to combine.

Step 3

Slice the potatoes in half lengthways, not cutting all the way through the skin at the bottom. Mash the flesh of the potatoes in the skin a little, then add butter to each half. Top with a generous scoop of tuna and a handful of watercress. Serves 2