Instructions

Make the Apple Filling (day 1)

1. Combine the apples with the sugar, cider, vanilla, cinnamon and salt. Set aside to macerate for at least 1 hour and as long as 3 hours. Drain the apples, saving the juice. Combine 1/4 cup of the juice with the corn starch. Set Aside.
2. Put the apples and the rest of the juice in a large saucepan. Cook over medium-high until the juices begin to boil. Reduce the heat to medium-low and continue cooking until the apples are crisp-tender, stirring often. The apples should still hold their shape. The exact time will depend on the type of apple, estimate 10 minutes.
3. Add the corn starch mixture to the apples. Increase the heat to medium-high and return to a boil, stirring constantly. Cook until the juices are slightly thickened and become translucent. Transfer the apple filling to a container and cool to room temperature. Chill until ready to use. The filling can be made 2-3 days ahead.

Make the dough (day 1)

1. In a large saucepan, bring the apple cider to a boil. Reduce the heat and simmer until the 4 cups of cider are reduced to 1 cup. Transfer the reduced cider to a bowl and add the butter to the cider so that it melts. Set the bowl aside until the reduced cider is cooled to about 110°F (a little warmer than body temp).
2. In the bowl of a stand mixer or in a large mixing bowl combine the warm water, yeast, and 1/2 cup of the flour. Mix until it forms a thick batter. Cover the bowl and set it aside for 30 minutes (while the cider is cooling).
3. With the mixer running on low, add the egg, cardamom, cinnamon, salt and cider to the batter. Add another 2 cups of flour and mix until it forms a thick batter.
4. Switch to the dough hook and add the remaining 1 1/4 cups of flour. The dough will start out quite sticky. Knead on medium low speed for 5 minutes (speed 2 on my stand mixer) until the dough clings to the hook and clears the sides of the bowl. If working by hand mix in as much of the flour by hand as you can then turn the dough out onto a floured surface and continue kneading in the remaining flour. Knead for 5 minutes. If you have a hard time working with the sticky dough you can sprinkle a few more tablespoons of flour as you knead.
5. Knead into a smooth ball. Place the dough into a lightly oiled bowl, turning once to coat the dough. Cover and set the dough aside at room temperature for 1-1.5 hours until it's doubled in volume.
6. Without kneading the dough (kneading will cause it to spring back as you cut) roll to 1/4"-1/2" thick on a lightly floured surface.
7. Use a 4" round cutter to cut donuts. Line the donuts on a well-oiled baking sheet, leaving space between the donuts for the dough to rise (I used 2 baking sheets). Reroll the scraps of dough and continue cutting donuts until all the dough is used up.
8. Brush the tops of the donuts lightly with oil. Cover the sheet pans with plastic wrap. If you'd like to make the donuts in the morning refrigerate the donuts overnight. If making the donuts the same day, continue with the next step now.

Make the Donuts (day 1 or 2)

1. Allow the donuts to rise until almost doubled in size, about 1 hour. The time will vary based on the temperature of the room and the temperature of your dough (if you refrigerated the dough overnight they may take longer to rise).
2. Meanwhile, heat 2 quarts of oil to 350F° in a large heavy pot. Fry the donuts a couple at a time, about 2-3 minutes per side, until golden brown and puffy.
3. As you take each donut out of the oil, immediately roll in the cinnamon sugar to coat. Set on a cooling rack while you fry the rest of the donuts.
4. Once the donuts are cool enough to handle, use a skewer to poke a hole in one end of the donut. Push the skewer until it's in the center of the donut and move it around to create a pocket in the donut. Use a piping bag with a large round tip to pipe the filling into each donut.
5. Best eaten warm or within a couple of hours of frying.