Preheat oven to 175°C (350°F). Line baking sheets with parchment paper.
In a large bowl, cream together the butter, brown sugar, and granulated sugar until light and fluffy (about 2-3 minutes).
Add the egg, vanilla extract, and pumpkin puree. Mix until smooth.
Dissolve the espresso powder in 1 tsp warm water and stir into the batter.
In a separate bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg and salt.
Gradually fold the dry ingredients into the wet mixture until just combined. The dough will be soft and sticky.
Scoop large mounds of dough (about 3 tbsp each) onto the baking sheets, spacing them about 5cm (2 inches) apart.
Bake for 12-14 minutes, or until the cookies are puffed and the edges are set.
Allow cookies to cool completely on a wire rack.