In a small saucepot add the heavy cream and the 4 cheeses, constantly stirring until fully melted and the sauce is smooth.

Add the remaining ingredients (pepper, salt, nutmeg, and optional truffle pieces).

For a super smooth sauce, blend with a hand stick blender.

Set the sauce aside while preparing the gnocchi, and reheat gently in a frying pan when ready.

Bake the potatoes with skin on in the oven at 176°C/350°F until very tender when pierced with a sharp knife, approximately 1 to 1.5 hours.

Carefully cut the potatoes in half lengthwise and let stand until cool enough to handle.

Peel the potatoes and discard the skins.

Press the potatoes through a potato ricer or fine mesh sieve over a bowl.

Add the egg, quickly mix in, and season with salt.

Add the flour gradually until the dough just comes together.

Divide the dough into 4 pieces, take one piece and cover the remaining pieces.

Roll out the dough, cut to shape, and transfer to a prepared baking sheet.

Repeat the rolling and cutting process with the remaining 3 dough pieces.

Bring salted water to a boil in a large pot.

Reduce the heat to a simmer, add all the gnocchi, and gently stir.

Cook until the gnocchi rises to the surface, then gently simmer for 1 minute, reducing heat as necessary to avoid a boil.

Drain well and add the gnocchi to the 4 cheese sauce.