For the pasta, place the flour into a food processor, crack in the eggs and pulse to combine. Add a little water, if necessary, to make the dough come together (the dough should ball together when you rub a piece between your fingers).
Turn the dough out onto a floured work surface and knead lightly for 2-3 minutes, or until smooth and elastic. Flatten out the dough and roll to a 1cm/½in thickness. Wrap the dough in clingfilm and leave to rest in the fridge for 30 minutes to relax.
Remove the cling film and cut the pasta dough into 2 equal pieces. Flatten each piece out slightly with a rolling pin the same width as your pasta machine.
Pass the dough through the pasta machine, starting with the thickest setting, then fold the ends of the pasta back into the middle, like a business letter. Turn 90 degrees and roll the pasta through the thickest setting once more. Change the setting on the pasta machine to the next thickeness and feed the dough through again. Repeat the rolling, passing the sheet through each setting until you reach the thinnest setting. Cut each sheet of pasta into 3 (the dough should yield enough pasta for approximately six sheets measuring 35cm x 10cm/14in x 4in).
Layer the sheets of pasta on a tray, separated by layers of cling film, and keep in the fridge until ready to use.
For the filling, heat the olive oil in a large frying pan over a high heat and fry the ceps with a pinch of sea salt and freshly ground black pepper for 2-3 minutes, until tender. If you are unable to find fresh ceps you could use either button or field mushrooms. Or you could use some good quality dried ceps, soaked in advance.
Add the shallots and cook for 1-2 minutes. Add the garlic, then mix the ceps and shallots together and cook for 1-2 minutes, or until the shallots are softened. Add the lemon juice and mix well. Remove from the heat and tip out onto a plate to cool down slightly, then chill in the fridge until cold.
Take one pasta sheet and place 4 large teaspoons of the filling along the middle, making sure the mounds of filling are evenly spaced. Lightly brush the pasta around the filling with egg wash. Fold the top edge of the sheet over the filling to meet the bottom edge of the sheet, then press around the filling with your fingers to seal (make sure there are no air bubbles in the pasta). Repeat with the remaining sheets of pasta and the filling.
Cut out the tortellini, using a medium size cutter to stamp out a half moon shape. Press the middle down lightly, then bring the bottom corners of the half-moon together to form a circle. Pinch the ends together to seal. Place the prepared tortellini onto a lightly floured plate until ready to cook.
Preheat the oven to 170C/340F/Gas 3.
For the roasted nuts and sage butter, scatter the pine nuts and hazelnuts on a baking tray and roast in the oven for about 10 minutes, or until the nuts are golden-brown. Remove and set aside to cool.
Cook the tortellini, in batches, in a pan of boiling salted water for 2-3 minutes, or until al dente. Remove with a slotted spoon and transfer to warm serving plates.
Meanwhile, heat the butter in a pan over a medium heat until melted and hazelnut-brown in colour (be careful not to let the butter darken beyond nut-brown). Add the sage and cook for 5 seconds, then pour in the water and a squeeze of lemon juice and cook for 1-2 minutes.
To serve, spoon the sage butter over the tortellini and scatter over the roasted pine nuts and hazelnuts.