Make the Truffle Dough: In a large bowl, beat together the butter and sugar until creamy. Mix in the cake mix, flour, salt, vanilla, and peppermint extract. Add milk gradually until the dough reaches a moldable consistency. Stir in green food coloring and sprinkles.
Form the Truffles: Roll the dough into small balls (about 1 inch in diameter) and place them on a parchment-lined baking sheet. Chill in the refrigerator for 15 minutes.
Melt the Chocolate: In a microwave-safe bowl, melt the chocolate coating in 30-second intervals, stirring in between until smooth.
Coat the Truffles: Dip each chilled truffle into the melted chocolate, ensuring it is fully coated. Place back on the parchment paper and immediately sprinkle with decorations before the chocolate sets.
Chill & Serve: Refrigerate the truffles until the chocolate has hardened, about 30 minutes. Serve chilled or at room temperature.