Ashton spotted a gap on the inside of England centre Brad Barritt and, having called for the inside ball, proceeded to lead the Ulster defence a merry dance as he weaved his way to the try line.
One of the defenders he turned inside out was 2009 Lion Tommy Bowe, who came onto the field as a second half replacement, and Saracens went on to win 27-16 to clinch a semi-final spot against either Toulon or Leicester Tigers at Twickenham later in the month.
Bowe's reappearance on the field after nearly four months on the sidelines with knee ligament damage will have pleased the on-looking Warren Gatland, who was also able to see two other international wings in action in the game in Ireland's Craig Gilroy and England's David Strettle.
Earlier in the European quarter-final weekend, Gatland had watched London Wasps duo Christian Wade and Tom Varndell race away for two tries each in their side's Amliin Challenge Cup defeat to Leinster. Ireland's Simon Zebo returns to the Munster line-up against Harlequins in the Heineken Cup today,
The Lions tour party for the game against the Barbarians in Hong Kong and nine matches in Australia is due to be announced on 30 April.