The 17-year-old scrum-half was called on to the bench by head coach Pat Howard after injury to Harry Ellis and he was able to experience the last 13 minutes of Saturday's 44-16 victory over Gloucester in front of a 59,000-strong crowd at Twickenham as Tigers sealed a league and cup double.
"You have to pinch yourself, it takes a while to sink in," said Youngs, who is not 18 until September.
Already Leicester's youngest-ever Premiership player, the son of former Tigers and England No.9 Nick Youngs and brother of centre Tom, is also now the youngest to play in a final.
"I had a few messages on my phone from family and friends, and a huge amount of support from senior guys like Ian Humphreys, Harry Ellis and Paul Burke," he said.
"When everybody was getting warmed up in the second half, Pat winked at me and said I would get on in five minutes. The butterflies kicked in but then I was just itching to get on.
"At the start of the season I just wanted to settle in and maybe push for a few games in the A League. That turned out all right and now I have been involved in a Guinness Premiership Final, it is a dream come true."
Youngs, who made his first senior outing against Argentina in February then made his league debut in the closing minutes of the match at Bristol last month, said the faith put in him by coaches Howard and Richard Cockerill had helped in the build-up to Saturday's Twickenham showdown.
"It was great for me thinking that if Frank Murphy had got injured then the coaches felt I would be able to cope," he said. "It does your confidence a lot of good when the coaches show faith in you like that."
Now there is another step up as Youngs will return for pre-season training as a member of the senior squad.