Beat the butter, pumpkin puree and sugar until smooth and fluffy.
Beat the egg yolk and pumpkin spice in to the above mix.
Sift the flour and baking powder and incorporate it in to the butter mix on low or with a wooden spoon.
Mix the flour in gently till you form a soft dough.
Form the dough in to a flat disc and wrap it in plastic wrap and refrigerate for at least one hour.
Roll out the dough to approximately 1/8 of an inch thickness between two parchment papers (to prevent sticking) or on a lightly floured countertop.
Preheat oven to 325°F
With a 2 inch cookie cutter, cut out cookies and place them gently on a parchment paper an inch apart. Re-roll the dough once to cut more cookies.
If the cookies get too soft, keep the dough in the freezer for a few minutes to harden so it is easier to handle.
Bake the cookies 10-15 minutes until the edges are crispy, and the middle is not too soft.
Remove from the oven and let the cookies cool on the baking tray for a few minutes before letting them cool on a wire rack.
When cookies are cooled completely store them in an air-tight container. These can be served as is, or with a dusting of icing sugar or with a mocha filling (Recipe follows)