Preheat oven to 180°C. Heat a nonstick pan with a generous amount of olive oil. Add the potatoes and sauté for about 12-15 minutes, until cooked. Add salt to the potatoes, remove from heat and set aside to cool.
Beat the egg with the olive oil and yogurt. In a separate bowl, mix the flour with the baking powder and combine with the egg mixture. Add the feta cheese, potatoes, bacon and sage, season with salt and pepper and mix well.
Fill 2/3 of greased muffin pots with the muffin mixture and bake for 25 minutes. Serve warm.