Preheat oven to 400ºF.
Slice a thin piece off of the tops of potatoes lengthwise – you want to slice off less than 1/4 of the potato. Scoop out the potato flesh from both cuts of the potato into a mixing bowl and transfer the potato boats to a baking sheet. With a fork or potato masher, smash up the potato in a bowl until somewhat smooth.
Place a medium-size skillet over medium high heat with 2 turns of the pan of EVOO, about 2 tablespoons. Add the onion, garlic, some salt and freshly ground black pepper. Cook, stirring every now and then, for 2-3 minutes, until the onions start to get tender.