Step 1
Heat hazelnut spread in metal bowl over saucepan of gently simmering water and stir until hazelnut spread is warm smooth and easily stirred about 5 minutes. Remove bowl from heat.
Step 2
Dissolve sugar in water in a small saucepan over medium heat. Brush sides of pan with a moistened pastry brush occasionally as sugar mixture cooks. Increase heat to medium-high and bring syrup to a boil and cook until syrup is a deep amber color brushing down sides and swirling saucepan occasionally to prevent scorching about 4 minutes.
Step 3
Pour cream into the syrup while stirring. Reduce heat to low and cook stirring continually until you have a smooth caramel 5 to 10 minutes; gently stir into the melted hazelnut spread with 1/4 teaspoon sea salt.
Step 4
Refrigerate caramel mixture until firm at least 3 hours.
Step 5
Spread cocoa powder into the bottom of a wide shallow bowl.
Step 6
Scoop caramel mixture with a melon baller into 1 tablespoon portions; roll in the cocoa powder to coat; arrange onto a baking sheet.
Step 7
Cover truffle balls with plastic wrap and chill overnight or 8 hours.
Step 8
Line a 13x9x2-inch baking sheet with aluminum foil.
Step 9
Heat chopped chocolate in a metal bowl set over a saucepan of gently simmering water stirring frequently until chocolate is melted and smooth and the chocolate reaches a temperature of 115 degrees F (46 degrees c). Remove bowl from over water.
Step 9
Working quickly submerge each truffle ball in the melted chocolate. Lift truffles from chocolate with a fork and tap fork against side of bowl to remove excess coating. Transfer truffle to foil-lined pan to cool. Repeat with remaining truffle balls.