Wrong answer to my question, gamemaster79...
Well, the question has become old now, so the right answer was
Mario & Luigi: Superstar Saga, and the means was the 'magic' machine in Hoohoo Village where Mario had to spit water into its fan to generate coins, and sometimes regular Mushrooms...
The process was really quite slow, and it does not make you rich any quicker...
I am a pure Super Mario lover!!
...and in no point in the future will he ever be abandonded by me!
I will even drawn the best Super Mario comics ever to exist!!