Way I did this was to set up a Team Jam Session (Note: must be Jam Session, cannot be done in pro-tour) with Cat and Mouse, and set the rounds to 5 or more. When 4 or more players have joined your session, start. The mouse selection is random, I have been the mouse twice in succession, while others have not been the mouse once in the 5+ games we played. Set it to more than one game so that you dont have to go back to the lobby over and over, just waste's time.
Winning isn't easy, you need to beat the other Mini, whilst avoiding getting the crap knocked out of you by the other team's Group B cars, but if you race clean and hope that your team is good at blocking, you'll get it no problem.
Please note!: Some have mentioned that if you do not join the game on the first round, you will not get the achievement. I personally did not have this problem, but please be aware of it if it does not unlock for you. - Thanks to I Anger I for pointing this out.