Put the cornmeal, flour, 1 tsp of the koshur salt, matcha powder and baking powder in a mixing bowl, and stir well with a whisk to blend.
In a separate bowl, whisk together the egg and water, then stir into the dry ingredients, mixing only until moistened. Sprinkle the remaining ˝ tsp koshur salt and the freshly ground pepper over the onion and sliced okra, and toss lightly. Fold the vegetables into the batter.
Pour 1 inch of oil into a heavy skillet and heat to 340°F. Spoon the okra batter by heaping tablespoons into the hot oil; do not overcrowd the pan. Fry until golden brown on one side, then carefully turn and continue frying until both sides are browned.
Remove from the skillet and drain well on a draining rack or crumpled paper towels.