In a small pot, cook the potatoes in boiling water until tender.
Take the potatoes out of the boiling water. Once they cool to the room temperature peel them and cut into slices.
Preheat oven to 350°F.
In a medium-size bowl, beat the eggs and season them with salt and pepper.
In a large ovenproof pan, heat the oil then add onion and garlic. Cook for a few minutes, stirring, until soft.
Pour in half of the egg mixture then place potato slices on top.
Sprinkle the cheese and pour the remaining egg mixture.
Cook on medium heat for 2-3 minutes until the eggs are set.
Transfer pan to the oven and bake for 10-15 minutes.
Cool frittata slightly then cut into slices and serve.