Finely chop the chocolate with a large, sharp knife.

Heat the heavy cream in a small saucepan until it barely starts to boil.  You will see steam first, then small bubbles.  Remove from heat immediately and pour in the chopped chocolate all at once.  Whisk until well blended.

Pour some ganache on a small plate to rim the martini glasses.  Pour the rest in a bowl to allow it to cool.

Pour some sprinkles on a small plate.

Dip the rim of the martini glass into the ganache first, then dip and twirl it in the sprinkles.

Squeeze some sauce in the corner of a plastic sandwich bag.  Twist the top and snip off the tip to form a small piping bag.

Starting at the bottom, squeeze the sauce into the martini glass and swirl upward until ½ inch from the rim.  Place in the freezer until needed.

Pour the sweetened condensed milk into the bowl of ganache and whisk until well combined.

Whisk in the coffee and vanilla extract, then taste and adjust flavors by adding more coffee or vanilla as desired.  Whisk in the optional cocoa powder.

Pour the mixture into a glass carafe or 4-cup jug with a spout to make it easier to pour into the decorated martini glasses.  Take the glasses out of the freezer and pour into two glasses.

If desired, place a small scoop of coffee ice cream in the drink.  Serve immediately.