1.Preheat oven to 200°C.
2.Pierce kumara all over with fork; place on oven tray. Roast 2 hours until very tender.
3.When kumara are cool enough to handle, peel, then chop coarsely. Using wooden spoon, push through fine sieve or mouli into large bowl. Stir in flour, yolks and cheese. Knead gently on floured surface until mixture comes together. Dough should be soft, pliable and slightly damp but not sticky.
4.Heat vegetable oil in frying pan; cook pancetta until crisp. Drain.
5.Divide dough into four portions. Roll each portion into 2cm thick log, then cut into 2cm lengths with sharp knife.
6.In a large saucepan of boiling water, cook gnocchi, in batches, about 2 minutes or until gnocchi float to surface. Remove gnocchi from pan with slotted spoon; drain. Gently toss gnocchi in large bowl with olive oil.
7.In a medium saucepan, melt butter, stirring, about 3 minutes or until butter foams then turns golden. Stir in garlic and ginger; remove pan from heat. Add to gnocchi with baby spinach and pancetta; toss gently to combine. Sprinkle with extra pickled ginger, if you like.
Do not overwork the dough or it will toughen.Note