In the bowl of a stand mixer, combine sweetened condensed milk, peppermint extract, and vanilla extract. With the mixer on low, gradually add half of the powdered sugar. Continue adding the rest of the powdered sugar bit by bit until a dough forms.

Sprinkle about 3 tablespoons of powdered sugar on a piece of parchment paper. Knead the dough a few times to ensure everything is well combined.

Roll the dough into a ½-inch thick circle, sprinkling powdered sugar on top to prevent sticking.

Use a 1 to 1 ½-inch cookie cutter (or the top of a small glass) to cut circles from the dough. If the dough becomes too warm and difficult to cut, place it in the freezer for 15 minutes and try again.

Move the peppermint patties to a parchment-lined baking sheet. Freeze for 15 minutes.

Melt the dark chocolate in the microwave in 30-second increments, stirring each time to prevent burning. Let it cool slightly for 3-4 minutes.

Using a fork, dip each peppermint patty into the melted chocolate, flip to coat both sides, and place it back on the parchment-lined baking sheet. If desired, top with sprinkles.

Refrigerate for 20 minutes to allow the chocolate to set before serving.