Preheat oven to 350°F. Grease a 6-cavity doughnut pan (or 2 pans if you have them).
In a large bowl, whisk together the dry ingredients (flour through nutmeg).
In another bowl, whisk together the egg and sugar. Whisk in the pumpkin puree, followed by the buttermilk and vanilla. Stir in butter.
Whisk wet ingredients into dry ingredients in 2-3 additions until just combined. Transfer batter to a piping bag or plastic Ziploc, and cut off the tip. Pipe half of the batter into the prepared pan, filling nearly to the top. Alternatively, you can fill the pan using two spoons, and then smooth out the top.
Bake on the center rack of the oven for 10-14 minutes, or until a toothpick inserted into the center comes out clean. Allow to cool in the pan for 5 minutes, then turn out onto a wire rack to cool completely. Repeat with remaining half of the batter.
When doughnuts are cooled, prepare the glaze. Place chopped chocolate in a bowl. Add cream and salt to a small pot and warm over medium heat. When cream comes to a simmer, remove from heat and pour over the chocolate. Allow to sit for about two minutes, then stir to combine. Cool slightly.
Dip the tops of the doughnuts into the glaze, flip and return to the wire rack. After dipping all of the doughnuts, sprinkle with the chopped nuts. Allow the glaze to cool at room temperature, then transfer to the fridge until the glaze sets completely. Enjoy.