The Derry super bantam moved up to six rounds for the first time to face experienced Nicaraguan Edwin Tellez at the Europa Hotel.
The toughest opponent of his professional career so far, McCullagh floored his opponent in the first en-route to a fourth round stoppage win.
White Chocolate made a measured start, boxing off the southpaw jab and countering sharply, and one such straight left counter downed Tellez at the end of the round.
McCullagh found the target with increasing regularity in the second, with some brilliant footwork opening up numerous opportunities and one crunching bodyshot in particular had the Central American wincing.
By the third it was total dominance for the Derry fan favourite who was landing at will, while Tellez could only resort to wild swinging counters and a few shots that bended the rules.
The fight would continue in the same vein in the fourth before the referee waved the bout off with Tellez offering little back in the face of continued, albeit measured, pressure from McCullagh
The stoppage win sees McCullagh move to 5(4)-0, while Tellez drops to 11(5)-26(4)-5 after a tough night’s work.