Prepare the candied walnuts:

1. Add the chopped walnuts, butter, and sugar to a nonstick pan and heat over medium heat stirring constantly for 3 to 4 minutes until sugar is melted.
2. Once cooled, further chop the walnuts into tiny pieces to sprinkle over the donuts. 

Prepare the glaze:

• Whisk the confectioners’ sugar, heavy cream, vanilla, cinnamon, nutmeg and cardamom in a small bowl until thoroughly combined.

Prepare the donut batter:

1. Preheat oven to 350 degrees.
2. Reduce the apple cider by 1/2 by simmering over medium heat in a pot on the stove until 1/2 cup of liquid remains. Mine took about 10 minutes to reduce.
3. Combine flour, baking powder, cinnamon, nutmeg, cardamom, salt and lemon zest in a medium bowl. 
4. Using a stand mixer with the paddle attachment, combine the melted butter, granulated sugar, brown sugar, buttermilk and vanilla. Once well mixed add the egg on low speed until just combined. 
5. Slowly add the dry ingredients to the wet ingredients with the mixer still set to low until well combined.
6. Pour the slightly cooled reduced apple cider into the mixture and mix.
7. Spoon your batter into a zip-lock bag, seal, and cut one of the bottom corners of the bag to squeeze the batter through into the pan.
8. Grease donut pans with nonstick cooking spray.
9. Fill each cavity of the donut pans about half way full and bake for approximately 10 minutes until cooked through.
    
10. Remove donuts while still hot and dunk each side into the glaze. Sprinkle the top with chopped candied walnuts.
11. Allow to cool on a cooling rack.