Prepare cupcakes as directed. 

While cupcakes bake, prepare pudding. In a medium bowl, sift together cocoa powder, cornstarch and salt. In a medium bowl or measuring cup, whisk together heavy cream and egg yolk. Pour liquid into cocoa mixture, mixing with a wooden spoon until smooth and thick. 

In a medium saucepan over medium heat, combine whole milk and sugar. Whisk gently to dissolve sugar. When bubbles form around the edge of the saucepan, remove from heat and whisk in thick cocoa mixture until smooth. Return to medium-high heat and bring to a boil. When large bubbles form, remove from heat, stir in chopped chocolate and mint extract. Whisk until completely smooth. Transfer to a clean bowl, press plastic wrap to the surface and cool to room temperature. 

Prepare whipped cream. In a medium bowl, beat together heavy cream and powdered sugar until nearly stiff peaks form. Transfer to the refrigerator until ready to use. 

If cupcakes have been dipped in ganache, slice off the top of at least 6 cupcakes. Cut the bottom portion into small pieces. 

Using desired individual serving dishes, create layers of cake, followed by pudding and whipped cream. Repeat until all ingredients have been used up. Cut up additional cupcakes as needed. Piping bags or spoons may be used to add both pudding and whipped cream to the serving dishes. Garnish with a single Thin Mint cookie. Enjoy immediately or chill until ready to serve.