Mix chocolate graham cracker crumbs with butter in a small bowl and press mixture onto bottoms of paper lined mini muffin cups.
In a large bowl, or bowl of stand mixer, beat together the cream cheese, sugar, and vanilla until well combined. Beat in egg just until blended.
Spoon cheesecake mixture into muffin cups, about 1 Tablespoon each.
Bake in preheated oven for 15 minutes. Remove from oven and top with chopped M&M's immediately. Cool the cheesecakes completely, then refrigerate for one hour.