Crush up about 4-5 ladyfingers in a Ziploc bag until you get what looks like breadcrumbs.
Add a small amount of corn syrup to a shallow dish that will fit the entire rim of your martini glass. Spread the corn syrup out in a very thin, even layer.
Dip the rim of the glass in the corn syrup and then into a shallow dish of the crushed ladyfinger cookies.
Add the vodka, cream, Tia Maria and dark rum to a cocktail shaker filled half way with ice. Shake well and strain into a martini glass.
Garnish with a ladyfinger and a dusting of cocoa powder.