In a large bowl, whisk together the cornmeal, flour, salt, baking powder, and sugar (if using).
In a small saucepan, bring the milk and water to a boil. Carefully pour into the cornmeal mixture and whisk until a thick, polenta-like batter forms.
Heat a No.9 Field Griddle or cast iron skillet over medium-low heat for a couple of minutes. Add about 3 tablespoons butter or bacon fat. Form the batter into golfball-size rounds, then pat into disks. Add 4 or 5 Johnnycakes to the skillet and press flat with a spatula. Cook cakes until golden brown on the bottom, 2 to 3 minutes, then flip and cook until golden brown on the other side, 2 to 3 minutes longer. Transfer to a platter and keep warm.
Repeat with the remaining batter, adding more butter or bacon fat as needed between batches. Serve hot with butter and syrup.
