Step 1

For potato and leek filling, simmer whole peeled potatoes from a cold start in a large saucepan of salted water until tender (20-30 minutes). Drain and set aside for a minute to allow excess moisture to evaporate. Pass potatoes through a potato ricer. Wash leeks well, remove green part and reserve, and thinly slice the white parts. Heat butter in a saucepan over medium heat and sauté leeks until soft and sweet (10-20 minutes). Add to potato, mix well, allow to cool, then add pecorino, season to taste, mix to combine and refrigerate until required.

Step 2

Preheat oven to 220C. Roast reserved potato peel until deep brown in colour (20-30 minutes).

Step 3

Heat oil in a saucepan over medium heat add shallots and garlic, and stir occasionally until caramelised (25-35 minutes). Add roasted potato skins and thyme, then cover with 1 litre of water. Bring to the boil and simmer over medium-high heat until the stock is nicely flavoured (30-40 minutes). Season to taste, strain (discard solids) and set aside.

Step 4

Reduce oven to 200C. Roast the green part of the leeks until brown and crisp (30-40 minutes; It doesn't matter if they burn a little). Cool slightly then process in a food processor or blender toa fine powder and set aside.

Step 5

Prepare pasta according to basic pasta recipe. It's important the pasta isn't thick or it won't cook evenly. Cut into 9cm squares, place on a tray and dust with a little flour and semolina. You can cover with plastic wrap to prevent drying. Forming a raviolo at a time, place a 4.5cm cutter in the middle of a pasta square, fill it with 1 tbsp potato mixture, pressing evenly into the ring. Remove cutter, brush pasta edges lightly with eggwhite, then stretch another pasta square over the top. Use the blunt side of a 5cm cutter and gently press down around the filling to create a tight seal, pushing any air bubbles out with your fingers. Leaving the 5cm cutter in place, use an 8cm cutter to trim raviolo into a round. Remove both cutters and use your fingers to make sure it's sealed tightly. Place raviolo on a tray lined with a tea towel dusted with semolina and repeat until all ingredients are used. You may have a little filling leftover; any extra pasta scraps can be reserved for making stracci (see stracci with hare and radicchio recipe).

Step 6

Cook ravioli in a large saucepan of boiling salted water until al dente and cooked through (3-5 minutes), then drain.

Step 7

Heat reserved stock to a simmer over medium heat. Make a slurry using potato starch and 1 tbsp water, and stir into stock to thicken to a sauce consistency. Makes about 500ml.

Step 8

Place a raviolo on each plate, drizzle with roast potato sauce and dust with powdered leek.