In a medium bowl, mix together flour, salt, and baking powder. Stir in mashed potatoes and onion until thoroughly combined.

In a separate bowl, whisk together eggs and milk, and stir lightly into potato mixture.

Stir in nutmeg, mixing well.

Heat a large griddle to medium-high heat. Brush the griddle with oil and spoon potato mixture onto griddle in 12 equal portions.

Fry until brown on both sides brushing the griddle with more oil as necessary. Serve hot.