Add the diced onion & sliced ham to a lightly-greased pan and cook until they become golden brown.
Lightly grease a muffin tin with some cooking oil and then scoop in your onion & ham mixture.
In a mixing bowl, add in your eggs, milk & baking powder and mix them together.
Carefully add the egg mixture into the muffin tin and add a handful of grated cheese to each muffin.
Place the muffin tin into a preheated oven at 190°C for 25 minutes.
Allow to cool for five minutes before serving.