In a small bowl, use an electric mixer to beat the cream until it has medium peaks- light and fluffy.
ASSEMBLE THE COCKTAIL:
Pour boiling water into a mug and let it sit for about 3 minutes to warm up the mug. Then dump it out. Add the whiskey and brown sugar to the mug. Pour the coffee on top. Give it a stir to dissolve the sugar. To put the whipped cream on top, turn a spoon upside down and pour the whipped cream over the back of the spoon, letting it fall into the mug. This allows the cream to float on top, rather than sinking to the bottom. Don't stir. This cocktail is meant to be sipped through the cream.
Notes
Use freshly brewed hot coffee for best flavor.
Don’t overwhip the cream—it should be soft and pourable so it floats.