Preheat oven to 150°C.
Place flour and salt in a large bowl for your electric mixer and whisk to remove lumps.
Pour in butter, water and two egg yolks. Beat into a smooth but thick batter. If necessary add in extra water. I have had to use up to an extra 1/3 cup at different times. Things like your flour, size of eggs etc affect how thick the batter will be.
Add ham, corn, shallots and cheese and mix gently by hand.
In a clean bowl beat the egg whites until stiff, stir gently in to the batter mix with a wooden spoon.
Heat 2 tablespoons of olive oil and 2 tablespoons of butter in a large frying pan.
Add 1/3 cup mixture to the pan to form each fritter. Cook for approximately 7-10 minutes each side until cooked through. To keep the fritters warm while you cook the remaining fritters place in the oven wrapped in foil. You may need to add more butter and oil during cooking.