The Fulham striker yesterday put pen to paper on an initial one-month deal after linking up with his new team-mates in training at Canford School.
Boss Lee Bradbury was delighted to bolster his attacking resources, having previously missed out on signing Middlesbrough's Jonathan Franks and West Brom frontman Simon Cox.
And Mitchell insists the move for the 19-year-old is a signal of Cherries' intent to last the distance in the League One promotion race.
Mitchell told the Echo: We know there are still 13 games of the season to go and we need every point we can get out of them, so we need goals.
It is not that we haven't got goalscorers because we would not be winning games otherwise. But it just gives other options and it shows our intent to keep us in contention.
Mitchell and Bradbury both confirmed that the chairman's son, Tom Mitchell, played a part in the recruitment of Dalla Valle.
Mitchell junior discovered that the striker was available and alerted Bradbury, leading to the Cherries boss doing his homework on the player before making his move.