Preheat a griddle to 325°F.
In a large bowl, whisk together the flour, baking powder, baking soda, pumpkin pie spice, salt, and brown sugar.
In a separate bowl, stir together the pumpkin puree, milk, eggs, melted butter, and molasses (if using).
Add the flour mixture to the pumpkin mixture, stirring by hand until just combined.
Using a ⅓ cup measuring cup, pour the thick pancake batter onto the griddle. Cook until the edges bubble slightly, 2-3 minutes. Then, flip over and cook the other side for another 2 minutes. Timing will depend on your griddle.
Serve pancakes warm with butter, maple syrup, and optional chopped pecans.