In a bowl place the eggs, the oil, the salt and mix very well for 2 minutes, until combined. Add the wheat flour, pass it through a sieve and add the corn starch, sift it too.
Gradually add the milk until it forms a batter, keep mixing well.
Add the diced ham but don't add all of it, save some for the end of the recipe. Add the mozzarella and do the same thing we did with the ham, set some aside. Add parsley and chives, the diced tomato and set some of these ingredients aside as well. Mix well until combined.
Add the baking powder and mix again.
Transfer the batter to a ring cake pan greased with butter and flour. Top it with the ingredients we've set aside and bake in a preheated oven at 200°C (392°F) for 40 to 50 minutes.
Do the toothpick test.
Serve.