Line a baking sheet with parchment paper or a silicone baking mat so the chocolate doesn’t stick.
Melt the milk chocolate in a heatproof bowl over a pot of simmering water (double boiler method) or in the microwave in 30-second intervals, stirring between each time until smooth.
Pour the melted chocolate onto the prepared baking sheet and spread it evenly with a spatula until it’s about ¼ inch thick.
Place the 12 mini pretzels on the chocolate for the reindeer antlers. Add the 12 red M&M's under the pretzels for the reindeer noses. Put the candy eyes above the noses to finish the reindeer faces.
Scatter the green M&M's and the sprinkles over the bark while the chocolate is still soft to give it extra festive color and texture. Let the chocolate sit at room temperature until it sets, or place it in the fridge for 20–30 minutes to speed it up.
Once the chocolate is firm, break it into pieces by hand. Enjoy your reindeer bark or pack it up as a holiday treat for friends and family.