1/3 oz grenadine syrup
1/3 oz creme de menthe
1/3 oz 151 proof rum

Divide a tall shot glass into thirds, fill the lowest third with grenadine syrup, the middle third with creme de menthe, and float the 151 in the top third.

Wet a thin straw, light the 151 by passing a lighter over it, plunge the straw to the bottom of the glass into the grenadine syrup and suck. If done rapidly and correctly the straw will not melt, and you can observe flames travelling up the inside of it. Stop sucking when the flame is inside the straw.