If using fresh truffles, brush them clean, wipe with a moist cloth, and pat dry. If using canned truffles, drain and pat them dry.

Grate the truffles very fine using the smallest holes of a flat-sided grater.

Lightly crush the garlic to loosen the peel, then peel and discard the skin.

Bring water to a lively simmer in a narrow saucepan (for a double boiler).

In another small saucepan, cook the olive oil and garlic over medium heat until the garlic turns light nut brown. Discard the garlic.

Set the oil pan over the simmering water. Add anchovy and mash it with the back of a wooden spoon until nearly dissolved. Return the pan to low heat and stir constantly a few minutes, until the anchovy is almost entirely a paste.

Stir in the grated truffles, taste and adjust salt if needed, stir quickly once more, then turn off the heat.

Toss hot drained spaghettini with the sauce. Drizzle a few drops of raw olive oil over the pasta and serve at once.