Discard the celery leaves, rinse the stalks and cut into strips, removing any tough fibres.
Put the celery in a casserole with 1/4 cup (4 tablespoons) of water.
Coverand microwave on HIGH for 10 minutes.
Leave to stand, covered, for 3 minutes.
Put the Mascarpone in a bowl with the sour cream (creme fraiche) and heat in the microwave oven on HIGH for 1 1/2 minutes until the cheese has melted.
Add several dashes of Tabasco sauce and the champagne.
Stir thoroughly.
Drain the celery, put in a vegetable dish, pour the sauce over, sprinkle with the chopped chervil and serve.
Mascarpone is a type of Gorgonzola with a very high cream content.
If it is not available, try for cambozola, or failing that use equal quantities of gorgonzola and cream cheese.