These truffles are inspired by brigadeiros, a confection popular throughout Brazil.
In a medium saucepan, bring condensed milk, butter, and cream to a boil over medium-high heat, stirring until butter melts. Cook, stirring frequently, until mixture thickens slightly and turns pale golden, 4 to 6 minutes (do not let it get too dark, or mixture will separate). Remove from heat; let stand 5 minutes. Add chocolate, cocoa powder, and vanilla, stirring until chocolate melts and mixture is smooth and combined. Transfer to a pie dish or a wide, shallow bowl and refrigerate until firm, about 4 hours.
Scoop 1 tablespoon of chocolate mixture into your palm and roll into a ball. Transfer to a parchment-lined baking sheet; repeat with remaining mixture. Place sprinkles in bowls (onefor each color). Roll truffles in sprinkles until thoroughly coated. Place in paper mini baking cups and serve, or store in refrigerator, covered, up to 1 month.