Anthony Irvine's side have had an indifferent season but they turned on the style to deservedly take their place in the final against old foes Elland.
There were plenty of fine performances but Chris Moran's three try haul coupled with an outstanding defensive effort saw him emerge as the Irish hero.
Irvine and Chris Norman also came up with great performances with the player coach leading by example.
Irish started the game at a high tempo and took an early lead as the impressive Chris Muxlow romped over, Martyn Silcox converting.
Nick Cassell and Joss Bentley were prominent in the early exchanges whilst Siddal's Jack Holmes and Richard Pearson looked the most likely to prise open the Irish defence.
Siddal then began to get into the game and raced into a 12-6 lead as scrum half Chris Brooke registered a quick fire double. Shaun Blackburn adding the extras to both tries.
Back came the visitors as Moran broke through a couple of tackles 20 metres from his own line, he raced clear and fended off several defenders for a fantastic solo try.
Young wingman Arran Illingworth then spotted the smallest of gaps and stretched out to score on the right flank.
Silcox added a fine conversion and a penalty soon after to put his side 20-12 up at the interval.
The second half was a bruising affair with both sides giving their all.
The first try was going to be crucial and it went to the Irish as once again that man Moran sped over. Silcox's conversion put his side 26-12 up and the holders had a mountain to climb.
Despite the efforts of Ian Crawshaw and Daz Phillips they could not find a way through the resolute defence.
As the game went into the closing stages it was no surprise when Moran crashed over.
Silcox's conversion left Irish celebrating their best performance of the season.

Brighouse Rangers 56 - Wortley Dragons 4
(Division Two)
Rangers kept the pressure on the other title contenders, never looking back after centre Chris Scrimshaw scored in the first minute and Gary Proctor converted.
Midway through the half Chris Gregg shrugged off numerous tackles to score and then winger Mark Horne touched down under the posts, Proctor's goals making it 18-0.
Rangers added another 16 points before the break thanks to tries from Liam Baker, Reece Spurr and Mark Barton, plus two more Proctor conversions.
There was a lull in the action in the third quarter and it took a Wortley try to stir the home side, who responded with tries from Scrimshaw, Baker, Carl Gregg and Barton, Proctor's eighth goal completing the scoring.