Whisk together flour, baking powder, baking soda, salt, cinnamon, and nutmeg in a large bowl.
In another bowl, combine pumpkin purée, brown sugar, eggs, vanilla, and milk until smooth.
Pour the wet ingredients into the dry mixture and stir gently until just combined. Do not overmix; a few lumps are fine.
Heat a non-stick griddle or pan over medium heat, adding a light coat of butter or oil.
Pour 1/4 cup of batter per pancake onto the pan, spreading slightly. Cook until bubbles form on the surface and the edges look set.
Flip carefully and cook the other side until golden brown and cooked through.
Repeat with remaining batter, keeping pancakes warm in a low oven while finishing the batch.
Serve stacked high with maple syrup, butter, or whipped cream, and a sprinkle of toasted pecans if desired.