1
: In a heat proof bowl, set over a saucepan of simmering water, melt the chocolate and butter. Stir to combine. Remove from heat and set aside.
2
: Beat sweetened condensed milk, egg and vanilla for 1 minute until well beaten. Add melted chocolate mixture. Beat in remaining dry ingredients. Batter will be very loose. Cover with plastic wrap and refrigerate 3 hours or up to overnight until mixture is firm enough to roll into balls.
3
: Preheat oven to 350ºF (180ºC). Line baking sheets with parchment paper.
4
: Place icing sugar in a shallow bowl. Roll dough in 1” (2.5cm) balls. Place the ball of dough into the icing sugar and roll in the sugar until completely coated and no chocolate shows through. Place on prepared baking sheet about 2” (5cm) apart.
5
: Bake in preheated oven 8-10 minutes or just until the edges are slightly firm but the centers are still soft. Cool on a wire rack.