In a 4-quart saucepan, combine Milk (2 cup),Heavy Cream (2 cup), and half of the Granulated Sugar (1 1/4 cup). Set over high heat, and cook, stirring occasionally, until mixture comes to a boil, about 5 minutes.
Meanwhile, in a medium bowl, whisk Egg (8) and remaining sugar until smooth, heavy, and pale yellow, about 30 seconds.
When cream mixture just comes to a boil, whisk, remove from heat, and in a slow stream, pour a ladle of the cream mixture over yolk-sugar mixture, whisking constantly until blended to temper the egg yolks.
Return pan to stovetop over low heat. Whisking constantly, stream yolk-cream mixture back into pan.
Continue stirring until mixture registers 165 to 180 degrees F (74 to 82 degrees C) on an instant-read thermometer, about 2 minutes. Do not heat above 180 degrees F (82 degrees C), or eggs in base will scramble.
Mixture should be slightly thickened and coat the back of the spoon, with steam rising, but not boiling. If you blow on the back of the spoon and the mixture ripples, you've got the right consistency.
Pour base into a clean container and refrigerate for 12 to 24 hours. Use base within 3 to 5 days.
Process the base in an ice cream maker according to manufacturer's instructions.
Add Bushmills® Irish Whiskey (1/4 cup) during last 2 minutes of churning.
Transfer to a bowl and fold in the Lucky Charms® Cereal (3/4 cup).
Scrape into an airtight storage container. Freeze for a minimum of 2 hours before serving. Serve on maple flapjack cookies for the perfect ice cream sandwich. Enjoy!