In a large bowl, whisk together the flour, sugar, baking powder, baking soda, and salt., In a separate bowl or large measuring cup, whisk together the egg, buttermilk, butter or oil, and vanilla., Pour the wet ingredients into the dry ingredients, stirring to combine. Stir until the mixture is fairly smooth; some small lumps are OK., Allow the batter to rest, uncovered, for 15 minutes., While the batter is resting, heat a large skillet over medium heat or preheat a griddle to 350°F, until the surface is hot enough for a droplet of water to skitter across it. Lightly grease the pan with butter or vegetable oil., Spoon the batter, 1/4 cup at a time, onto the hot surface; a scone and muffin scoop works well here., Cook pancakes on the first side until bubbles form on the tops and the bottoms are brown, about 1 to 2 minutes. Flip and cook until the bottoms are brown, 1 to 2 minutes longer., Serve immediately, or hold briefly in a warm oven., Leftover pancakes can be frozen the same day they're made and reheated in a 250°F oven.