Tip the potatoes into a large pan, cover with cold water and sprinkle with a generous pinch of salt. Set the pan over a high heat and bring to the boil. Once boiling, reduce the heat to a simmer and cook for 15-20 mins until the potatoes are very tender – they should be able to be easily pierced with the tip of a knife. Drain well, then return to the pan and leave to steam-dry for 5 mins.

Pass the potatoes through a ricer into a large bowl for a lump-free mash (you may need to do this in batches). Alternatively, mash with a potato masher until smooth, then press through a sieve using the back of a spoon to get rid of any remaining lumps.

Tip the 50g salted butter, the milk and some seasoning into the bowl with the hot mash. Beat everything together with a wooden spoon or spatula until the butter has melted and the mixture is smooth and creamy. Add a splash more milk to loosen, if needed. Top with the remaining 1 tbsp butter and leave it to melt for a few seconds before serving.