Mix the mascarpone, cheese, semolina and egg yolk in a bowl, roughly grate in the pear, season with chilli flakes and salt.
Unroll the pasta dough, cut in half lengthwise. Place 8 portions of the filling on half of the pasta strips at equal intervals.
Brush the remaining strips of pasta with a little egg white.
Place on top of the filling, press the edges down firmly, pressing out any trapped air.
Separate the ravioli using a pastry wheel, press the edges down firmly with a fork.
Coarsely chop the walnuts, dry-roast the nuts in a non-stick frying pan until golden brown. Remove the thyme leaves, add to the pan along with the butter, heat through until the butter foams and smells slightly nutty and the thyme is crispy.
Cook the ravioli in batches in simmering salted water for approx. 5 mins. Remove the ravioli with a slotted spoon, drain, add to the butter and mix carefully.