Put the chopped chocolate in a small heatproof bowl. Warm the cream with the salt in a 1-quart / 1 L saucepan over medium-low heat for 2 to 3 minutes, until steam rises and tiny bubbles form at the edges. Pour it over the chocolate, wait 1 minute, then stir in the honey until glossy. Pour into a 10 cm / 4-inch ramekin and freeze for 30 minutes, until stiff but still scoopable.

While the ganache chills, tear six 20 cm / 8-inch squares of plastic wrap and press one into each cup of a 6-cup muffin tin, leaving the edges hanging over. Move both tubs of gelato from the freezer to the fridge for 15 minutes, until you can press a spoon into them but they're still cold and not runny.

Scoop the ganache into six portions of about 1 tbsp (18 g) and roll each into a ball with cold hands, dusting your fingers with cocoa if it sticks. Set the balls on a small plate and return them to the freezer.

Press 40 g of hazelnut gelato into each lined cup, pushing it up the sides, and make a small well in the center with the back of a spoon. Set a ganache ball in each well, then cover with 40 g of chocolate gelato and smooth the top. If the gelato turns glossy and runny at any point, return it to the freezer for 20 minutes before continuing, because melted and refrozen gelato turns icy.

Gather the plastic wrap over each cup and twist it closed so the gelato forms a tight ball. Set the wrapped balls back in the tin and freeze for 2 hours at -18 C / 0 F, until solid all the way through.

Sift the cocoa onto a plate. Unwrap one truffle at a time, roll it in the cocoa, and press gently between your palms to smooth the coating. Twist each into a square of wax paper, return it to the freezer, and serve after 5 minutes at room temperature.