Place chopped chocolate, cream and butter in a medium heat-proof bowl. Microwave in 20-second intervals, stirring in between each interval, until melted. Alternatively, set it over a saucepan of simmering water, stirring occasionally. Stir in lemon zest (from 3 lemons) and lemon juice. Cover the bowl and chill in the refrigerator for at least 3 hours or until firm.
Combine powdered sugar and zest (from 1 lemon) in a small bowl, tossing it well with your fingers or a fork. Take chocolate mixture out of the fridge. Using a small ice cream scoop, teaspoon, or melon baller, scoop out small sections and form them into balls with your hands (mine were 12g each, 1-inch in diameter, but you can make them any size you want). If they are soft, place in the refrigerator until firm. Roll each ball in the sugar-lemon mixture and place on a baking sheet lined with parchment paper. Refrigerate until firm.
Store truffles in the refrigerator in an airtight container for up to a week. Serve chilled.