Finely chop 8 ounces of Valrhona 56% chocolate and place in a large bowl.

Boil 2/3 cup of heavy cream in a heavy-bottomed small pan. Boil it three times, cooling it between simmerings.

Pour the hot heavy cream over the chopped chocolate, mashing any big pieces with a spoon.

Stir the mixture in concentric circles starting in the center and working your way to the edge with a whisk until it forms a smooth ganache. Avoid incorporating air and creating bubbles.

Let the ganache stand at room temperature until thick enough to hold a shape, about 1 hour.

Using a pastry bag with a 3/8-inch opening or tip, pipe the ganache into mounds about 3/4 inch high and 1 inch wide on parchment-lined baking sheets. Finish each mound with a flick of the wrist to soften and angle the point tip. Freeze until firm, about 15 minutes.

Melt 3 more ounces of Valrhona 56% chocolate. Smear some of the melted chocolate on a gloved hand.

Gently rub each chilled truffle in the melted chocolate to coat it lightly.

Toss each coated truffle in a bowl of unsweetened Valrhona cocoa powder using a fork until covered.

Shake truffles in a sieve to eliminate excess cocoa powder.

Store truffles in the refrigerator. Pack them in gift boxes if desired.