Easy Chocolate Truffles

1. In a medium sauce pan combine the sweetened condensed milk, chocolate chunks, cocoa powder, espresso powder (if using), and salt. Place over medium-high heat and bring to a gentle boil, stirring constantly. Reduce heat to medium-low and cook for 5-8 minutes, stirring constantly, until mixture is thick and starts to pull away from bottom and side of sauce pot. 
2. Remove from the heat and stir in the butter and vanilla. Pour mixture into a bowl, cover, and chill for 1 1/2 hours or overnight. 
3. Place the sprinkles/chocolate in a shallow bowl. Rub a small amount of softened butter over your hands and scoop out rounded teaspoons of the chocolate mix. Roll into balls in the sprinkles or chocolate. Place on a baking sheet lined with parchment paper.
4. Store in the refrigerator for up to 1 week.