Tau was instrumental in setting his side on their way to a famous 3-0 win over Belgian First Division giants Anderlecht in the Croky Cup Last 32 tie on Thursday evening.
The 24-year-old, who is on loan from Premier League side Brighton & Hove Albion for the season, picked up a clearance from a corner at the edge of his box to launch a menacing counter-attack.
He proceeded towards the opposing goal while shrugging off his marker, before neatly placing a perfectly weighted pass for striker Youssouf Niakate to bag the opener in the 44th minute.
He was substituted out after 67 minutes as coach Luka Elsner looked to reserve his legs for their league tie against Oud-Heverlee Leuven on Sunday afternoon.
Niakate later completed his hat-trick to ensure St Gilloise advance to the Last 16 of the competition for the first time in over 14 years.
Tau, who scored in the previous round against City Pirates, will have another opportunity to continue his impressive cup run against Royal Knokke FC in the first week of December.
WATCH: Percy Tau assist vs Anderlecht