For the filling:
4.5 oz. good quality white chocolate, very finely chopped
Zest of 1 lemon
3 tbsp. heavy cream
6 oz. bittersweet chocolate, finely chopped
2 tsp. canola or vegetable oil (optional)
step 1: Show Images
Place the chopped white chocolate and lemon zest in a heatproof bowl. In a small saucepan, heat the heavy cream to a simmer. Pour the hot cream over the chocolate and let sit 1-2 minutes. Whisk the mixture together to melt as much of the chocolate as possible. If there are still small pieces of unmelted chocolate, microwave in 10-15 second intervals, stirring in between, until the mixture is completely smooth. Cover and refrigerate until the mixture is firm and scoopable, about 2-3 hours.
step 2: Show Images
Using a small scoop or measuring spoon, scoop a small amount of the filling mixture and roll into a smooth ball, about ¾-1 inch in diameter. Transfer the shaped balls to a flat plate or baking sheet lined with a silicone mat or parchment paper. Chill for 30 minutes.
step 3: Show Images
To coat the truffles, melt the bittersweet chocolate in a heatproof bowl set over simmering water. Mix in the oil, if using. (You may want to transfer the melted chocolate to a small, deep bowl for easier dipping.) Quickly dip a filling ball into the chocolate and remove, gently shaking off the excess. Return the filling ball to the baking sheet and repeat with the remaining balls until all are coated. Chill to set the coating, at least 30 minutes.