Combine sweetened condensed milk, peppermint extract, and vanilla in a stand mixer, then gradually mix in powdered sugar until a dough forms.

Sprinkle powdered sugar on parchment paper, knead the dough until smooth, and roll it to ½-inch thickness, dusting with more sugar to prevent sticking.

Cut into small circles with a cookie cutter or glass; if the dough softens, freeze for 15 minutes before cutting. Arrange patties on a parchment-lined sheet and freeze for another 15 minutes.

Melt dark chocolate in 30-second microwave intervals, stirring until smooth, then let cool for 3–4 minutes.

Dip each patty in chocolate with a fork, coat both sides, and return to the sheet. Add sprinkles if you like.

Refrigerate for 20 minutes until the chocolate sets, then serve chilled or at room temperature.