In a large bowl, whisk together the flour, sugar, baking soda, baking powder, and salt. Then stir in the oats.
In a separate medium bowl, whisk together the buttermilk, eggs, melted butter, and vanilla.
Add the wet ingredients to the dry and whisk briefly just until blended. Then let the batter stand to thicken, at least 2 hours. (Overnight is ideal. Cover the batter and refrigerate.)
When you are ready to cook the pancakes, heat a griddle or skillet over medium heat. Then melt some butter across the surface.
Working in batches, ladle the batter by ¼ to ⅓ cupfuls onto the preheated surface. (Adding a bit more butter for each batch, as necessary.) Cook until bubbles have formed on top of the pancakes and the bottoms are golden brown, about 2 to 3 minutes. Turn the pancakes over and cook until the other side is golden brown, about 2 or 3 minutes more.
Serve immediately, either with pure maple syrup or generous dollops of lingonberry sauce and whipped cream.