To make the gnocchi, place the walnuts in a food processor and blend. Add the flour and cooked butternut squash and blend together.
Divide the mixture into 4 and toss in plain flour. Roll each into a long, thin sausage, then chop into 2.5cm/1in pieces. Toss again in flour to coat, then drop into a pan of boiling water.
After a minute the gnocchi should float to the surface. Remove with a slotted spoon and set aside.
To make the sage butter, melt the butter in a frying pan, then add the sage leaves. Fry for a minute to infuse, then add the gnocchi and toss together.
Serve the gnocchi in a warm bowl and season well with salt and freshly ground black pepper.