{blackbabes} Nicki Minaj -- BREAST BDAY CAKE EVAHH!!

Nicki Minaj turned 31 years old yesterday -- and she celebrated with two voluptuous helpings of BOOB CAKE!!!

After arriving in a hot pink Lambo, the rapper strolled into Philippe restaurant in Bev Hills last night (probably because her manager is partial owner of the joint) ... where she partied with friends like 16-year-old Kylie Jenner.

We're guessing Minaj served appetizers, and maybe even dinner, inside the venue ... but it didn't really matter -- everyone was focused on dessert.