Preheat your oven to 375 degrees F, and line 2 large baking sheets with parchment paper or silicone baking mats. Set aside.
To the bowl of your stand mixer, with paddle attachment fixed, add the butter and sugars. Mix until smooth. Next, add your egg and mix again until incorporated. Add the pumpkin puree and vanilla extract, and mix again until smooth.
In a large bowl, whisk together the flour, baking soda, baking powder, cinnamon, salt, allspice, ground cloves, and ground nutmeg. Fold in the rolled oats.
With the mixer speed set on low, slowly add the dry ingredients to the wet. Mix until just combined. Do not over-mix.
Fold in the coconut, hazelnuts and chocolate chips until evenly dispersed.
Scoop the cookie dough onto the prepared baking sheets in 2 tablespoon dollops. Bake the cookies for 10-11 minutes or until the edges just begin to brown, but the center is still soft. Remove from oven and set aside to cool for 2-3 minutes. Transfer to a wire rack to cool the rest of the way.
While your cookies are cooling, prepare your glaze. To a double boiler, add the white chocolate chips and the whole milk. Whisk until melted. Remove from heat, and whisk in the confectioner's sugar until smooth. If you find that the glaze is too thick, add a touch more milk. If you find that it is too thin, add tablespoons of confectioner's sugar until you reach the desired consistency.
Drizzle the glaze onto cooled cookies. Serve immediately or store in an airtight container for 2-3 days.