Preheat oven to 350F (175C).

Bake the sweet potatoes in the preheated oven for 20-30 minutes or until tender.  Allow to cool, and then peel and cut into 1/4 inch slices.

Beat eggs whites and the whole eggs in a small bowl. Season with salt and pepper.

Heat half of the olive oil in a large oven-safe pan or skillet.

Add the onions and saute until browned.  Season with additional salt and pepper to taste. Allow to cool.

Return pan to the stove on medium heat.  Add the remaining olive oil. Add a layer of the sliced sweet potatoes, followed by one third of the yellow peppers, red peppers, parsely, and Swiss chard.  Pour a third of the egg mixture over the vegetables.  Make additional layers, until all of the remaining ingredients are used and in the pan.  Press the layers down, if needed, to ensure the egg mixture covers the ingredients.

Place the pan in the preheated oven for 20 - 25 minutes or until the eggs are set and the top is golden brown.

Remove from the oven and allow to cool for 5 minutes before slicing and serving.