Caramel-dark chocolate truffles with fleur de sel

Place 224g (8oz) chocolate in metal bowl over saucepan of barely simmering water (do not allow bottom of bowl to touch water); stir until chocolate is smooth. Remove chocolate from over water.

Combine sugar and 2 tablespoons water in small saucepan. Stir over medium heat until sugar dissolves, occasionally brushing sides of pan with wet pastry brush. Increase heat; boil until syrup is deep amber color, brushing down sides and swirling pan occasionally, about 4 minutes. Add cream (mixture will bubble). Stir over very low heat until caramel is smooth. Mix caramel and ¼ teaspoon fleur de sel into melted chocolate. Chill until truffle filling is firm, at least 3 hours.

Place cocoa in bowl. Using 1 tablespoon truffle filling for each truffle, roll into balls, then roll in cocoa. Arrange on baking sheet. Cover; chill overnight.

Line a 32x22x5cm (13x9x2-in) baking sheet with foil. Place remaining 336g (12oz) chocolate in medium metal or glass bowl over saucepan of barely simmering water (do not allow bottom of bowl to touch water); stir until chocolate is melted and smooth and thermometer inserted into chocolate registers 46°C/115°F. Remove bowl from over water. Working quickly, submerge 1 truffle in melted chocolate.

Using fork, lift out truffle and tap fork against side of bowl to allow excess coating to drip off. Transfer truffle to prepared sheet. Repeat with remaining truffles. Sprinkle truffles lightly with additional fleur de sel while coating is still wet. Let stand until coating sets, at least 1 hour. (Can be made 1 week ahead. Cover and chill. Bring to room temperature before serving.)