Porthcawl were 27-5 up thanks to Jordan Fox’s stunning first-half hat-trick and for large parts of the game his team looked certain winners.
But Pembroke came roaring back and took the lead midway through the second half for the first time.
A brace of tries from Sam Smith and efforts from Dom Colman, Dan Colley and Tom Lewis did the damage, but just when they looked like they’d lost the game, Porthcawl won it at the death.
Pembroke were penalised for a high tackle and the nerveless White stepped up to slot the penalty and send those of a green and black persuasion wild with delight.
It was harsh on Pembroke, but when the dust settles on this result both teams can be proud of their performance on the big stage.
Porthcawl made an electric start to score two early tries.
At the home of Welsh rugby, it was the Seaweeds who got the scoreboard moving, a fine team move involving Jon Phillips starting when a loose ball was picked up.
Flanker Ben Asprea was the beneficiary as he dived over, fly-half White adding the simple conversion. It soon got better for Porthcawl, too.
Centre Gareth Rees – who had an excellent game alongside his midfield partner Phillips – broke clear and right wing Fox finished off the move in the right corner.
This time, White couldn’t convert.
At 12-0 down, Pembroke looked up against it but they responded impressively.
The West Wales outfit pounded away at their opposition’s line and a try looked certain when a cross-kick found Rhodri Walters in acres of space. The flanker, though, knocked-on with the line gaping.
Still, Pembroke got their rewards when Colman crossed following a lovely pop pass from right wing Barrie Alderman-John. The try was unconverted.
The scoring continued as Alderman-John then turned from creator to villain.
The Pembroke man was yellow carded for a dangerous tackle on Phillips and his team paid the price, White kicking the resulting penalty and then with Porthcawl boasting a numerical advantage, wing Fox dived over in the right corner to make it 20-5 with just 25 minutes played.
Even with Alderman-John back on the field, more superb work from Phillips allowed Fox to complete his treble and White kicked the extras only for Pembroke tries from Smith and Colley plus one conversion from Shaun Dalling to give the men in red hope at the break.
When the game resumed White’s nerveless drop goal settled any Porthcawl nerves and the rate of scoring slowed, even if the spectacle continued to thrill.
Pembroke nonetheless refused to go away and after a stunning break from full-back Luke Hartland, Smith crashed over for his second of the day from close range.
Hartland added the extras to set up a thrilling final quarter with just six points between the teams.
With captain Scott Powell substituted and cheering on his Pembroke team from the stands, the comeback was finally complete as the West Wales side moved into the lead for their first time.
Left wing Elliot Evans did superbly to offload out of the tackle and find scrum-half Lewis. Toby Smith kicked the goal and Pembroke suddenly sensed glory.
Porthcawl chased the game and Jordan Skidmore pushed an effort for what would have been a winning drop goal wide as Pembroke looked like they’d edge the encounter.
But there was still time for yet more drama as White’s penalty edged things in Porthcawl’s favour.
