Preheat the oven to 325 degrees F. Butter an 8 x 8 cake pan and line with parchment paper, set aside.
Melt the butter and set aside.
Beat the egg yolks and powdered sugar until pale and light, about 5-6 minutes.
Mix in the melted butter and combine.
Add the flour mixing well to break down any lumps. Beat in the milk and vanilla.
Add the pumpkin, pumpkin spice and cinnamon and whisk until smooth.
In another bowl whip the two egg whites until stiff peaks.
Slowly add the egg whites whisking gently until smooth.
Pour the batter into the prepared pan.
Set the pan on a baking tray and bake for about 50-60 minutes. The top will still be a little jiggly but will set upon cooling.
Cool completely before slicing into small squares and drizzling with the spice glaze.
Combine the powdered sugar, pie spice and milk in a bowl and mix together with a fork.
Place in the microwave and warm for 20-25 seconds until it becomes a thin pourable consistency.
Drizzle the icing over each square and serve.