Lightly oil a large baking sheet; set aside.

Put sugar, butter, juice and 3 tablespoons water into a large skillet and bring to a boil over medium-high heat.

Continue boiling, stirring often, until golden brown and thickened, 3 to 4 minutes more.

Add walnuts, toss to coat and reduce heat to medium.

Cook walnuts, continually tossing them gently with a stir-frying motion, until coated and golden brown. The liquid will evaporate from the skillet and what remains appears powdery, but keep going.

Soon afterwards, the sugar will melt and caramelize.

When it's just melted and the walnuts are coated with deep brown caramel, 13 to 15 minutes total, turn off the heat.

Working very quickly, sprinkle zest, salt and cloves over walnuts, toss a few more times to distribute them evenly, then carefully transfer to prepared baking sheet. (Keep in mind that the walnuts are very hot!)

Using two forks, gently separate walnuts as much as possible then set aside to let cool completely.

Melt the chocolate in a double boiler over medium-low heat or in the microwave for about 1 minute, stirring often to keep the chocolate from burning.

Drizzle chocolate over cooled walnuts then set aside to let chocolate set. (Refrigerate them briefly to speed up the process, if needed.)

Store walnuts in an airtight container until ready to serve.