Place the potatoes in a saucepan with enough water to cover, bring to a boil and cook for 9-10 minutes until just tender, then drain.
Melt two tablespoons of butter in a large frying pan over low-medium heat. Add in the onions and cook for about 10 minutes, until just tender but not browned.
Place the potato slices in an even layer on top of the onions then pour 2 tablespoons of melted butter over the potatoes.
Mix together the chickpea flour, salt, pepper, and water in a separate bowl. Pour over the potato-onion mix to cover; make sure it seeps through to the bottom of the pan.
Continue to cook for 5 minutes or until mixture sets around the edges. Loosen the edges from the pan, then turn it out onto a large plate.
Heat remaining butter in the frying pan, then slide the frittata back into the pan, and cook for another 12-15 minutes until the bottom is golden brown and crisp.
* Percent Daily Values are based on a 2000 calorie diet. Some amino acids levels are estimated, some product manufacturers do not supply amino acid values. The value source usda.gov.