Boateng was indefinitely suspended by Bundesliga outfit Schalke in May and the Ghana international is now training with Milan until the end of 2015 as he searches for a new team.
The 28-year-old, who is contracted to Schalke until the end of this season, has been tipped to join Milan permanently in January, having spent three years at the San Siro before moving to the Veltins-Arena in 2013.
And the former Tottenham Hotspur and Portsmouth man did not dampen speculation in an interview with Sky Sport, saying: "I'm fine, I'm happy to have this opportunity to train. Milanello is my home.
"I like to be here and Milan is the team of my heart.
"I asked this favour and I made a little dream."
Boateng made 74 Serie A appearances and scored 10 goals in three seasons at Milan, winning the Scudetto and Supercoppa Italiana, before moving to Gelsenkirchen.