Knead the flour and eggs with a pinch of salt, cover with a tea towel and leave to rest for about 30 minutes. in the meantime wash the spinach and trim from the stalk. cook in a pan for about 1 minute, with a drizzle of extra virgin olive oil and a pinch of salt. remove from heat and allow to cool down. chop roughly and mix well with fresh ricotta. add two handfuls of grated grana padano cheese, a pinch of salt, black pepper and a little grated nutmeg. put the filling into a piping bag. with the help of a pasta machine, roll the pasta out. pass the dough through the narrower setting to make very thin pasta sheets. cut the pasta in 12 centimetre disks. create in each pasta disk a “cirle” of filling large enough to hold an egg yolk. gently place an egg yolk on each disk, and sprinkle with a pinch of salt. brush the edge of the pasta disk with water. cover with another disk and seal the edges. trim the edges of the raviolo with a knife. bring a pot of water to boil. before lowering the raviolo into the boiling water, melt butter on high heat in a separate casserole until brown. drop the raviolo into salted boiling water. cook for approximately 2 minutes, depending on the thickness of the ravioli. do not cook for more than 3 minutes. drain after and place gently into a deep plate. sprinkle with abundant grana padano, shaved truffle and finish with a nice spoonful of brown butter. the egg yolk should be runny, giving its flavour to the dish.