Peel and cut potatoes in cubes.  Place potatoes in a large heavy pot, cover with cold water.  Cook over medium hight heat until fork tender.

When potatoes are almost done peel onion and slice in half and cut into thin slices.  To carmelize onions put 4 Tablespoons of the olive oil in a pan over medium-high heat. Add onions and saute until they start to carmelize.  Make sure you stir.  This will take about 10 minutes.  At the last minute add the garlic.

Drain potatoes, reserving some of the potatoe liquid.  Add the other 4 Tablespoons of olive oil, salt and pepper , mash potatoes.  Stir in enough potato mixture to smooth out potatoes. 

Stir onions and garlic to the mashed potatoes.