The home side was boosted by a 10th minute John Murphy goal but Cuala, with David Treacy converting frees and Con O’Callaghan dangerous near goal, were 0-6 to 1-2 in front by the 20th minute.
By half-time, Cuala led 0-9 to 1-3 and were headed for a final showdown with Kilkenny’s O’Loughlin Gaels when O’Callaghan benefitted from a St Mullins defensive slip-up to goal on 48 minutes as the Dublin side led 1-11 to 1-4.
From there on, Cuala were in charge with Paul Schutte hugely impressive at centre-back.
The St Mullins challenge evaporated in the final 20 minutes as Cuala turned on the style, the home side losing captain Jack Kavanagh to a second yellow card in the dying stages as the favourites earned a shot at redemption after a heavy provincial final defeat last year to Oulart-The Ballagh.
D Treacy (0-7, 5 frees); C O’Callaghan (1-3); S Treacy (0-3); M Schutte (0-2), J Malone, D O’Connell, C Cronin, C Sheanon (0-1 each)
J Doyle (0-3, 1 free); John Murphy (1-0); J Kavanagh, M Kavanagh (1 free) (0-2 each).
S Brennan; O Gough, C O’Callaghan, S Timlin; S Moran, P Schutte, J Sheanan; J Malone, D O’Connell; C Waldron, C Cronin, D Treacy; C O’Callaghan, M Schutte, S Treacy.
C Sheanon for Waldron (49); R Tierney for S Treacy (55); S Stapleton for J Sheanon (55); N Carthy for Cronin (59); B Fitzgerald for D Treacy (59).
K Kehoe; G Bennett, J Doran, P Doyle; D Whelan, P Kehoe, G Cody; J Kavanagh, M Walsh, John (Minor) Murphy, S Murphy, John Murphy; M Kavanagh, J Walsh, J Doyle.
C Kavanagh for J (Minor) Murphy (h/t); P Connors for J Walsh (49).
P Burke (Kilkenny).