Preheat waffle maker on medium-high heat and oven to 200°F (93°C). Place a wire rack on a baking sheet and set aside.
In a large bowl, whisk flour, baking powder, baking soda, ginger, cinnamon, allspice, cloves, nutmeg, and salt.
In another bowl, whisk melted butter, brown sugar, molasses, eggs, and buttermilk until combined.
Pour wet ingredients into dry ingredients and gently mix until just combined. Small lumps are fine.
Grease waffle maker and pour about 1/3 cup of batter into each well. Close the lid and cook for 4–5 minutes until crisp.
Transfer waffles to the wire rack in the oven to keep warm. Repeat with remaining batter.
For the maple pecan topping, toast pecans in a skillet over medium-low heat for 4–5 minutes, then add maple syrup and heat for 1 minute.
Serve waffles immediately with warm maple pecan syrup or your favorite toppings.