Mashed Potatoes and Gravy

Method

1. 1Use starchy or all-purpose potatoes: russets give a light, fluffy mash, Yukon Golds a denser and more buttery one. Peel 1.4 kg and cut them into even chunks of 4 to 5 cm so they all cook at the same speed. Put them in a large pot, cover with cold water by about 2.5 cm and add 3 teaspoons of the salt. Starting in cold water lets the heat reach the centre of each chunk before the outside falls apart.
2. 2Bring the pot to a boil over high heat, then turn it down to a gentle simmer and cook for 15 to 20 minutes. The potatoes are done when a small knife slides into the largest chunk with no resistance and the chunk slips off the blade by itself. A rolling boil knocks the pieces around and breaks up the edges, so keep the water just bubbling.
3. 3While the potatoes simmer, start the gravy. Melt 45 g of the butter in a medium saucepan over medium heat, add the 35 g of flour and whisk without stopping for 3 to 4 minutes. The roux is ready when it turns golden brown, about the colour of peanut butter, and smells toasted. This step cooks out the raw flour taste and gives a gravy made without meat most of its colour.
4. 4Pour about 100 ml of the broth into the roux and whisk until you have a smooth, thick paste, then add the rest in a thin stream, whisking all the time. Adding the liquid slowly is what keeps lumps from forming. Bring it to a boil, lower the heat and simmer for 8 to 10 minutes, whisking often, until the gravy has reduced to about 500 ml and coats the back of a spoon. Stir in the soy sauce. If you have pan juices from a roast turkey, skim off the fat and use up to 200 ml of the juices in place of the same amount of broth.
5. 5Drain the potatoes well and tip them back into the hot, empty pot. Leave them off the heat for 1 to 2 minutes until the steam dies down and the surfaces look dry and chalky. Water left on the potatoes thins the mash and dulls its taste. Meanwhile warm the milk in a small pan until it steams but does not boil.
6. 6Mash the potatoes while they are hot, either through a ricer back into the pot or with a hand masher; cold potatoes turn gummy. Add the remaining 115 g of butter in pieces and fold it in until it melts, then add 300 ml of the warm milk in three parts, folding gently with a spatula after each. Season with the last teaspoon of salt. Stop as soon as the mash is smooth: every extra stir releases more starch, and a blender or food processor makes paste out of it in seconds. If the mash is stiffer than you like, loosen it with the remaining 60 ml of milk.
7. 7Taste the gravy only now and season it with pepper and, if it needs it, salt. Reduced broth and turkey juices are already salty, so salting earlier is the easy way to overdo it. If you see lumps, pour the gravy through a sieve. Bring it back to a bubble, spoon the potatoes into a warm bowl, make a well in the middle and pour in some of the gravy. Serve the rest in a jug.