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 egg with olive oil and yogurt. In a separate bowl, mix the flour with the baking powder and combine with egg mixture. Add feta cheese, potatoes, bacon and sage, season with salt and pepper and mix well.
Fill 2/3 of greased muffin pots with muffin mixture and bake for 25 minutes.