1. Line an 8-inch square pan with nonstick foil. Line a large baking sheet with parchment or wax paper. Heat 2/3 cup heavy cream and 2 tbsp coffee liqueur just to a simmer. Add 6 oz semisweet chocolate, 8 oz bittersweet chocolate, 2/3 cup confectioners' sugar and 1/4 tsp salt to a food processor. Whirl 1 to 2 minutes until ground. With machine running, add cream mixture in a steady stream; process until smooth. Scrape into pan; chill 11/2 hours. Lift from pan using foil. Cut into 36 pieces. Shape into balls. Place on parchment or wax paper-lined sheet. Chill 15 minutes. Re-roll truffles to smooth any rough edges, if needed. Sift 1/2 cup unsweetened cocoa powder into one bowl; place 1/2 cup confectioners' sugar in a second. Add truffles, a few at a time; toss to coat. Transfer each to a small paper or foil cup. Store in an airtight container up to 1 month.