Obtain two large metal mugs. In one, add Scotch and boiling water. Ignite the Scotch. Toss the hot mixture back and forth between the mugs a few times - it should look like you're pouring a liquid stream of fire. Extinguish the flames, add the sugar, stir to dissolve, pour into a tumbler. Add garnish.
Professor Thomas says to practice with cold water first lest you scald yourself.