Line an 8" x 8" baking pan with foil and set aside.
Melt Chocolate:
In a 2-quart saucepan over low heat, melt the coarsely chopped chocolate, cubed butter, and salt, stirring frequently until smooth, about 8 to 10 minutes.
Transfer the mixture to a food processor and set aside.
Prepare Egg Yolk Mixture:
Place the egg yolks in a mixing bowl.
While whisking constantly, slowly pour in ½ cup boiling water.
Strain the egg yolk mixture and add it to the chocolate mixture in the food processor.
Puree until smooth.
Chill Mixture:
Spread the chocolate mixture evenly into the prepared baking pan.
Chill in the refrigerator until firm, about 1 hour.
Form Truffles:
Place the Dutch-process cocoa powder in a bowl.
Invert the firm chocolate block onto a cutting board and discard the foil.
Cut the chocolate into 1-inch squares.
Toss the chocolate squares in the cocoa powder until coated.
Arrange the coated truffles in a single layer on a parchment paper-lined baking sheet and chill until set, about 10 to 15 minutes.
Notes / Tips / Wine Advice:
Wine Pairing:
Pair these truffles with a rich, full-bodied red wine like a Cabernet Sauvignon or a Port to enhance the deep chocolate flavors.