1 1/2 - 2 cups dried porcini mushrooms
1.8 kg (4 lb) white-fleshed potatoes (about 8), cut into 1.5 cm (1/2 in) cubes (I use desiree or toolangi delight potatoes).
40 g (1 1/2 oz/1 bunch) sage, leaves picked
140 ml (4 1/2 floz) extra-virgin olive oil
2 large brown onions, finely chopped
Sea salt flakes
75 g (2 3/4 oz/ 1/2 cup) 00 flour
1 egg yolk
Cover the porcini with water in a small saucepan over a high heat. Bring to the boil,remove from the heat and allow to sit for 10 minutes until softened. Remove the porcini from the water and finely chop. Set aside.
Cover the potatoes with cold water in a saucepan, salt the water and set over a high heat. Bring to the boil, reduce the heat to medium and allow to gently boil until soft, about 20–25 minutes.
While the potatoes are cooking, make the stuffing. Finely chop half the sage leaves.Pour 2 tablespoons of the olive oil into a frying pan and set over a medium heat.Add the onion, porcini mushrooms and finely chopped sage, and fry until golden,about 5 minutes. Season with sea salt and freshly ground black pepper. Remove from the heat and set aside.
Drain the potatoes and mash. Pass through a drum sieve into a bowl. If you don’t have a drum sieve, use a regular sieve or a potato masher to turn the potatoes into a smooth mash. Add the flour, egg yolk and a pinch of salt and stir to combine. Do not overwork the potato dough as it will become very gluey and starchy.
Lay a large piece of plastic wrap on a work surface. Spray with olive oil to prevent sticking. Spread one-quarter of the potato mix onto the plastic in a rectangular shape approximately 10 cm × 28 cm (4 in × 11 in) with a 1 cm (1/2 in) thickness. Spread one-quarter of the stuffing mix along the length and roll tightly in the plastic wrap. Twist the ends to secure, and seal by tying with cooking string to make a tight, firm roll. Repeat with the remaining mixture, using one-quarter quantities each time to make four rolls.
Bring a saucepan or large deep frying pan of water to the boil over a high heat. Add the potato rolls and cook until set, about 10–12 minutes. Remove from the water and allow to sit for 10 minutes.
Unwrap and cut the rolls into 2 cm (3/4 in) thick slices. Pour the remaining olive oil into a frying pan and set over a medium heat. Add the gnocchi slices and fry until lightly browned on both sides. Remove from the frying pan and set aside, keeping warm.Add the remaining sage leaves to the frying pan and cook until crispy, about 1–2 minutes. Season with sea salt and remove from the heat.
To serve, place the gnocchi slices in a bowl with the crispy sage leaves.