1. Heat oven to 200 degrees F. Combine flour, sugar, baking powder, baking soda and salt in a large bowl. Whisk until blended. Combine buttermilk, milk, eggs and melted butter in a medium bowl. Whisk until blended.
2. Heat a large nonstick griddle according to the manufacturers instructions. (Or heat a nonstick skillet over medium-high heat.) When griddle is hot, add buttermilk mixture to dry ingredients; vigorously mix batter with a wooden spoon just until blended. If lumps of flour are visible, thats okay.
3. Reduce heat to medium and grease griddle with butter, oil or shortening. Using a ladle or a 1/3-cup dry measure, pour spoonfuls of batter a few inches apart onto the hot greased griddle. Cook until small bubbles begin to form on the top and some pop, 2 to 3 minutes. Carefully turn pancakes with a flexible spatula, then cook 1 to 2 minutes more, until golden brown. Serve immediately with maple syrup and additional butter, if desired (or keep pancakes warm in oven). Repeat process with remaining batter.