1 cup strong freshly brewed hot coffee (usually decaf since this is sort of an after-dinner drink — I recommend the Fair Trade Decaf French Roast at TJ's — best if you can grind freshly)
2 tsp brown sugar
1 jigger irish whiskey (1.5 oz or 3 Tbs)
Heavy cream, lightly whipped (it's surprising how quickly you can do this by hand)
Preheat mug with hot water, then empty.
Put the brown sugar in the mug
Pour piping hot coffee (e.g. 4oz from a pod machine, or stored in a Thermal dispenser "Airpot") into warmed mug until glass is about 3/4 full.
Stir until the sugar is completely dissolved.
Blend in Irish whisky.
Top with a collar of the whipped heavy cream by pouring gently over back of spoon — don't stir, you'll drink the irish coffe through the cream.
Serve hot.
See posts on mugs: Thermal mugs and Classic, jumbo, & stacking ceramic mugs (though thermal is better!)