Reduce Apple Cider (Prep Ahead): Pour 3 cups of apple cider into a large saucepan. Bring to a boil over high heat, then reduce heat slightly to maintain a strong simmer. Cook until the cider is reduced down to 1 cup. This will take 15 to 20 minutes. Let the reduction cool completely. (This step concentrates the flavor and is crucial).

Make Doughnut Dough:

• Combine Wet Ingredients: In a medium bowl, whisk together the 1 cup cooled apple cider reduction, eggs, egg yolk, vanilla extract, and melted butter until combined.
• Combine Dry Ingredients: In a separate large bowl, whisk together the flour, cinnamon, cardamom, allspice, nutmeg, brown sugar, baking powder, baking soda, and salt until well combined.
• Combine Wet and Dry: Pour the cider mixture into the dry ingredients. Mix with a rubber spatula until just combined and a soft, slightly sticky dough forms. Do not overmix.
• Chill Dough: Cover the bowl tightly with plastic wrap and chill in the refrigerator for at least 1 hour (or up to overnight). Chilling is essential for handling this soft dough.  

Prepare Sugar Coating: While the dough chills or just before frying, combine the granulated sugar, 1 tablespoon cinnamon, 1/2 teaspoon cardamom, and 1/4 teaspoon allspice in a shallow dish or a large ziplock bag. Mix or shake until well combined. Set aside.

Prepare for Frying: Heat the canola oil in a large, heavy-bottomed pot or Dutch oven over medium to medium-high heat until it reaches 365°F (185°C) on a candy/deep fry thermometer. Line a large baking sheet or wire rack with several layers of paper towels for draining the doughnuts.

Roll and Cut Doughnuts: Divide the chilled dough in half. Working with one half at a time (keep the other half refrigerated), place the dough on a well-floured work surface. Roll the dough out to about ½-inch thickness. Cut out doughnuts using a floured 3-inch doughnut cutter. Place the cut doughnuts and doughnut holes onto a lightly floured baking sheet. Repeat with the remaining dough half, re-rolling scraps gently only once if needed.

Fry Doughnuts: Carefully place 3-4 doughnuts (and/or several doughnut holes) into the hot oil, being careful not to overcrowd the pot. Fry until golden brown, about 45 seconds to 1 minute per side. Use a slotted spoon or spider skimmer to carefully flip the doughnuts halfway through.

Drain: Remove the fried doughnuts from the oil and let them drain on the prepared paper towel-lined baking sheet or rack for about 30 seconds.  

Coat Doughnuts: While the doughnuts are still hot, carefully toss them in the prepared apple spice sugar mixture until generously coated. Place coated doughnuts on a wire rack.

Repeat: Continue frying and coating the remaining doughnuts and holes in batches, ensuring the oil temperature returns to 365°F (185°C) between batches.

Serve: Enjoy the doughnuts warm!