It's hard to give a quantity for truffles. Not only do truffles vary in degree of strength, they also vary in cost. So use as many as you can afford or think you need.
Ingredients
1.2 kilos of Potatoes
1 egg
400 grams / 3/4 pound flour
salt
200 grams / 1/2 pound taleggio
240 ml / 1/2 pint of heavy cream
3 tablespoons unsalted butter
Fresh truffle (as much as you can afford)
Instructions
The night before, grate some of the truffle into some softened butter and mix it well. Place in a non-reactive bowl and wrap tightly with saran wrap. Let sit for at least 24 hours to develop flavor.
Prepare the potatoes: wash them but do not peal them, and put them in a pot large enough to hold them and cover with salted cold water. Turn on the heat and bring to simmer, and cook until done.
While still warm (just let them cool off enough to not burn your fingers) peel them, and pass them through a potato press.
Add the flour, the egg and salt to the potatoes and mix until you get a mixture without lumps. Be careful not over mix.
Form long rolls of dough, rolling them out on a floured work surface. Let them rest a few minutes while you prepare the fondue.
Heat the heavy cream over a low flame, then add the cheese which has been cut up into small squares. Once melted, add a bit of grated fresh truffle.
Cook the gnocchi in boiling salted water. Add a handful of gnocchi at a time, and when they rise to the surface, scoop them up with a slotted spoon, letting the water drain
Add them to the fondue to reheat, using a bit of the gnocchi cooking water to loosen the sauce. Add 3 to 4 tablespoons of truffle butter and stir. Serve topped with grated white truffle.
Recipe by Elizabeth Minchilli at https://www.elizabethminchilli.com/2014/10/gnocchi-truffles-cheese-fondue/