Melt butter in a frying pan over medium-high heat and sauté the shallot for about two minutes until soft and fragrant. Add lemon peel and season with salt and pepper to taste. Add Prosecco and lemon juice, bring to boil and lower heat to medium. Simmer for a couple of minutes, add crème fraiche, stir well and cook for a few more minutes until slightly thickened.
In the meantime, cook the tortelloni for two minutes in a large pot of salted boiling water. Strain delicately with a skimmer and tip them into the pan along with two tbsp of pasta cooking water. Mix delicately.
Divide between two plates, garnish with chives and serve.