The Ghanaian international, who has been frozen out of recent Ghana games, came off the bench at Lecce with Milan down by three goals to spark a revival that saw reigning champions win 4-3.
Boateng's first arrived four minutes after he was introduced at half-time before adding two more on 55 and 63 minutes.
It capped a good week for the midfielder, who has now scored four goals in two games for Milan after his cracking effort in midweek for them in the Champions League.
But in Italy it is Udinese setting the pace aided by their Ghanaian pair of Kwadwo Asamoah and Emmanuel Agyemang Badu in midfield.
Both played the full game as Udinese beat Novara 3-0 to go to the top of the standings.
Elsewhere, Palermo midfielder Afriyie Acquah played for 80 minutes as his side went down 0-1 at AS Roma.