Place 8 ounces chocolate in metal bowl over saucepan of barely simmering water, do not let the bottom of the bowl touch the water, stir until chocolate is smooth. Remove the bowl of melted chocolate from over water and set aside.

In a small saucepan combine sugar and 2 tablespoons water. Stir the mixture 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, the mixture will bubble. Stir over very low heat until caramel is smooth. Mix the caramel and 1/4 teaspoon fleur de sel into the 8 oz. of melted chocolate.

Chill until the truffle filling is firm, at least 3 hours.

Place unsweetened cocoa powder in a bowl. Using 1 tablespoon or a small ice cream scoop of truffle filling for each truffle, roll into balls, then roll in cocoa. Arrange the truffles on a baking sheet. Cover with plastic wrap and chill overnight.

Line 13x9x2-inch baking sheet with foil.

Place remaining 12 ounces of chocolate in medium metal bowl over a saucepan of barely simmering water (do not allow bottom of bowl to touch water).

Stir until chocolate is melted and smooth and a candy or instant read thermometer inserted into chocolate registers 115°F.

Removethe  bowl from over water. Working quickly, dip 1 truffle at a time in  the melted chocolate.

Using a fork, lift out the truffle and tap the fork against the side of bowl to allow excess chocolate to drip off.

Place the truffle on the prepared baking sheet. Sprinkle truffles lightly with fleur de sel. Repeat with remaining truffles. Let stand until chocolate sets, at least 1 hour.

The truffles can be made 1 week ahead. Cover and chill. Bring to room temperature before serving.