In a large mixing bowl, whisk together the mashed sweet potatoes, milk, egg, melted butter, and vanilla extract until smooth.
In another bowl, combine the flour, sugar, baking powder, and salt.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Do not overmix.
Heat a griddle or skillet over medium heat and lightly grease it. Pour ¼ cup of batter for each pancake onto the griddle.
Cook until bubbles form on the surface of the pancakes and the edges look set, about 2-3 minutes. Flip and cook for another 2-3 minutes until golden brown.