Cut the breast into half horizontally to make 4 thin pieces, flatten, marinate with salt, pepper and paprika ½ tsp each.
In a bowl beat egg, milk, and water. In another bowl mix both the flour, powder milk, sugar, baking soda, mustard powder, remaining salt, pepper and paprika, dip chicken in egg mixture then in flour mixture, deep fry in fry pan until golden brown about 3 mins on each side.
Heat buns, spread with butter and spread 2 slices of pickled cucumber, top with fried chicken, cheese slice, tomato slice, top with bun, serve immediately with fries.