What's more decadent than a truffle? One that's enrobed in chocolate.
Butter an 8-inch square pan; line bottom with parchment. Chop chocolate into 1/4-inch pieces; place in a large heat-proof bowl.
Bring cream to a boil over medium-high heat; pour directly over chopped chocolate. Allow to sit for 10 minutes; use a rubber spatula to stir chocolate and cream until totally combined. Pour mixture into prepared pan. Cover with plastic wrap; chill until mixture is cold and set, 30 to 45 minutes.
Turn ganache onto a cutting board. Using a very sharp knife, trim edges to form right angles. Cut into 7 strips about 7/8 inch wide. Cut strips crosswise to form cubes. Place on a parchment-lined tray; chill for 5 minutes if soft, otherwise proceed to next step.
Once chocolate is tempered, use it immediately. Drop truffles into tempered chocolate one at a time; turn over to completely cover. Use a chocolate-dipping fork to lift truffle out. Tap fork; allow excess to drip back into bowl. With a second dipping fork, slide truffle onto a parchment-lined tray. Working as quickly as possible, repeat with remaining truffles (if tempered chocolate cools too much, it goes out of temper). When all truffles are dipped, you may drizzle with excess tempered chocolate.
Allow truffles to sit for at least an hour or overnight to fully set. Store at room temperature in a cool dry place.
Tempering chocolate requires measuring temperatures exactly with a chocolate thermometer. To get a clean cut, you may have to rechill truffle mixture periodically to keep it at the temperature that's easiest to work with.