Remove the crab meat from the shell. Break the meat apart with your hands.
In a large skillet, melt the butter, thyme, salt and pepper. Saute for about two minutes. Add the white wine and then the juice of the lemon. Cook for one additional minute. Remove from heat and let cool.
For the pasta:
Make a mound with the flour, plus a pinch of salt. Then make a well in the middle in which to put the eggs. Beat the eggs with a fork and then slowly use the fork to incorporate the flour. Once the eggs are absorbed, use your hands to knead the dough for 10 minutes until smooth. (Of course, you can use a kitchen mixer with a knead attachment to accomplish the foregoing.) Wrap the dough tightly in plastic and set aside for 20 minutes.
Cut the dough into 4-6 pieces of equal size, but use only one piece at a time (leaving the remaining dough wrapped in plastic). If you are doing this the old fashion way, with a rolling pin, then roll it out, fold it back several times, and continue this process until thin. Alternatively, pass it through a pasta machine until thin (or until it goes through the second thinnest setting at least twice). Take the sheet, and using a cookie cutter or glass of about 2 1/2 to 3 inches in diameter, cut the pasta into circles.
Immediately, spoon in the filling, and dab the edges with egg yolk. Fold in half and seal with fingers or a fork, and then fold again to form the tortelli. Repeat this process until all of the dough and filling are used.
For the finish:
Bring a large pot of salted water to a boil. Cook the tortelli for a few minutes and drain.
In the meantime, melt butter in a large skillet. Add fresh herbs basil, thyme, parsley, mint) salt and pepper and heavy cream to make a sauce. Add the tortelli when they are cooked and saute for about a minute. Serve immediately with a some fresh black pepper.
The use of prepared fresh pasta sheets will cut prep time by 30 minutes.