You can make your own pancake mix by combining the dry ingredients and storing them at room temperature in a resealable bag until ready to use.
In a medium bowl, mix flour, nonfat dry milk, sugar, baking powder, and salt.
Heat grill to medium. Place a cast-iron griddle on grill. In a medium bowl, combine 4 tablespoons melted butter and dry ingredients. Mix in eggs and 1 1/4 cup plus 2 tablespoons cold water. Stir until just combined; batter will be slightly lumpy.
Test griddle heat by sprinkling a few drops of water on it: If water bounces and spatters, it is ready. Add remaining 1/2 tablespoon butter to griddle. Pour a scant 1/4 cup batter per pancake onto griddle, and cook until surface bubbles and edges are slightly dry, about 2 minutes. Flip pancakes, and cook until undersides are golden brown. Repeat with remaining batter. Serve pancakes immediately with syrup and berries, if desired.