A first goal in United colours for the 20-year-old on-loan Fulham striker arrived against the run of play in the 13th minute.
Nick Ross equalised for Inverness in the 16th minute, but a mistake by Roman Golobart allowed Danny Swanson to restore the hosts' lead just before half-time.
United made sure of the triumph in the 71st minute, with Jon Daly coming off the bench to score his fourth goal of the campaign.
United manager Peter Houston had resisted the temptation to throw captain Daly straight back into his starting line-up following his rapid return from a knee ligament injury.
Fellow forward Johnny Russell was suspended following his dismissal in the 1-0 defeat to Rangers, while Sean Dillon joined Scott Severin on the casualty list.
For Caley Thistle, David Proctor won himself a place on the bench after recovering from a hamstring problem.
Inverness, however, were still missing six players - Josh Meekings, Chris Hogg, Lee Cox, Owain Tudur Jones, Aaron Doran and Jonny Hayes - through injury.
The visitors were looking for their first Clydesdale Bank Premier League victory on the road since overcoming Hamilton 2-1 on the final day of last season, and they started positively at Tannadice.
Gregory Tade forced Dusan Pernis into a save at his near post before Andrew Shinnie's close-range header from the Frenchman's cross narrowly went the wrong side of the post.
Inverness were undone by a slick passing move from United.
Willo Flood found Scott Robertson 25 yards from goal and he in turn slipped in Dalla Valle, who from an acute angle fired low past Ryan Esson.
United's lead, however, lasted only three minutes.
Shinnie was given far too much time and space inside the box and his low ball across the goal was converted by Nick Ross from less than two yards.
A powerful run from on-loan Wolves midfielder David Davis then had United's rearguard backtracking, but Pernis came to the rescue with a good block.
The home side had barely been seen as an attacking force, although Richie Foran was at full stretch to prevent Dalla Valle heading in.
Dalla Valle was proving to be a real handful for the visiting defence and Esson had to move quickly off his line to block the Finn's shot after he had met John Rankin's quick free-kick.
United finished the first half the better and Danny Swanson was a yard away from restoring their lead, but his shot from the angle of the box whistled by the upright.
Two minutes before the interval, a moment of hesitancy by Golobart gifted United back the advantage.
Attempting to deal with a high ball, he was caught in possession by Swanson, who calmly lobbed Esson from 14 yards.
It was to be Golobart's last contribution as he was replaced at half-time by Proctor.
The change failed to affect the momentum built up by United just before the break, however, and Rankin forced a fine save from Esson, who was also at full stretch moments later to keep out Gavin Gunning's shot from long range.
Shane Sutherland was introduced to the action in place of Foran as Caley Thistle attempted to muster an equaliser for a second time.
It so nearly arrived through Tade as he collected a fine pass from Davis, but Pernis stood firm at his near post to make the block.
United introduced Daly into the action and he made an immediate impact, his header from Paul Dixon's corner - the striker's first touch - giving the home side a two-goal cushion.
Inverness attempted to get themselves back into the game, but there were no further goals as United claimed all three points.