1. Read the gnocchi packet instructions before starting, as cooking times vary. Finely grate the Parmesan and have the butter, sage and truffle sauce ready. Bring a large saucepan of water to the boil and salt it lightly. Have two warm serving bowls ready.
2. While the water heats, melt the butter in a large frying pan over a medium-low heat. Add the sage leaves and cook gently for 1–2 minutes, until fragrant. The butter should foam gently without turning dark brown. Remove the frying pan from the heat and leave the sage in the butter.
3. Add the gnocchi to the boiling water and stir gently once to separate them. Cook for the time stated on the packet. Gnocchi often rise to the surface as they cook, but follow the packet instructions rather than using floating alone as the signal to remove them. Towards the end of cooking, carefully scoop 150 ml of the cooking water into a heatproof jug.
4. Just before the gnocchi is ready, return the frying pan to a low heat and carefully stir 2 tbsp of the reserved cooking water into the sage butter. Once the gnocchi has finished cooking, transfer it straight into the frying pan using a slotted spoon. Gently stir for approximately 30 seconds to coat, taking care not to break the gnocchi.
5. Remove the frying pan from the heat. Stir in 2 tbsp of Summer Black Truffle Sauce, then add the finely grated Parmesan in two additions, stirring gently after each. Add more reserved cooking water, 1 tbsp at a time, until the sauce lightly coats the gnocchi. It should look glossy, with no dry clumps of cheese or pool of watery sauce. You may not need all the reserved water.
6. Taste before adding salt, as the Parmesan and truffle sauce already contribute seasoning. Add freshly ground black pepper and up to 1 tbsp more truffle sauce if desired. Divide immediately between the warm bowls, spoon over any remaining sauce and sage leaves, and finish with a little extra Parmesan. Serve straight away, as the sauce thickens as it stands.
