Add confectioner's sugar 1/2 cup at a time, until incorporated.
Add vanilla.
Add in cream or milk until you get consistency you want.
Refrigerate until ready for use. Take out about 20 minutes ahead and pipe on top of cupcakes. I use a 1M jumbo tip to make the frosting look like ice cream. Don't pile too high because the ganache is rich.
Ganache
Chop chocolate, place in small bowl.
Heat cream in sauce pan just until boiling.
Pour over chocolate. Allow to sit for 2 minutes.
Stir from center until chocolate is melted.
Add in light corn syrup. Set aside to cool.
Assemble cupcakes
Frost cupcakes. Refrigerate for 30 minutes.
Prepare ganache and allow to cool, but not so much it hardens. If it does harden, soften by placing in microwave 10 seconds at a time. It should soften right up.
Pour ganache over frosted cakes to resemble a hot fudge.
Top with a sprinkles and a cherry.
Notes
This cupcake recipe makes 4 dozen medium cupcakes, plan accordingly. I usually make the whole batch and freeze the extra cupcakes unfrosted for future use.