Heat the oil in a non-stick pan over medium-high heat.
Add the potato and onion slices, stir to mix and coat with oil.
Add the garlic and mix in.
Cover and let cook until potatoes are soft, about 15 minutes, stirring occasionally.
Put the sliced chard on top of the potatoes and cover.
Cook another couple of minutes so the chard wilts.
Pour the beaten eggs over the chard and cover, cooking another 5-8 minutes, or until the eggs are mostly set.
Loosen the edges with a spatula and carefully slide the torta onto a plate.
Put the pan on top of the plate and invert so that the torta is back in the pan upside-down.
Cover and cook a few more minutes, until the eggs are cooked through.
Slice and serve.