Heat the fat in a saucepan. Sweat flour in it. Deglaze with cream and milk while stirring, bring to the boil. Wash the lemon well, rub dry, peel fine strips from the peel with a julienne shredder or peel the peel thinly and cut into strips. Add to the boiling sauce.
Halve the lemon and squeeze 1 half. Season the sauce with lemon juice, salt and pepper and simmer for another 5 minutes. Stir occasionally. In the meantime heat up tortelloni in plenty of boiling salted water for 1-2 minutes. Cut ham into thin strips. Remove the sauce from the stove, stir in the egg yolk, do not let it boil any more. Add the ham. Drain tortelloni. Arrange on plates.
Remove the sauce from the stove, stir in the egg yolk, do not let it boil any more. Add the ham. Drain tortelloni. Arrange on plates. Wash the basil, dab dry and remove the leaves from the stems. Cover with the sauce and sprinkle with basil leaves and parmesan
Per portion ca 2310 kJ/ 550 kcal