What's better than a warm doughnut on a cool day?
Combine 2 cups flour, undissolved yeast, sugar, salt and cinnamon in a large mixer bowl. Heat milk and butter to very warm (120°F to 130°F). Add to flour mixture with egg yolks; beat for 2 minutes at low speed. Continue adding flour until soft dough forms.
Knead on a lightly floured surface until smooth and elastic (about 4 to 6 minutes). Cover and let rest for 10 minutes. Roll out dough on a lightly floured counter into a 12-inch circle, about 1/2-inch thick. Using a 3-inch cookie or biscuit cutter, cut out as many rounds as possible. Cut out center with a 1-inch cookie cutter or poke hole through the center with finger. Place doughnuts about 2 to 3 inches apart on lightly greased or parchment lined baking sheet. Re-roll and cut remaining dough. Cover doughnuts and let rise for 45 minutes to 1 hour.
Heat at least 2 inches of oil in a deep fryer or deep pan to 350°F. Fry 2 to 3 doughnuts at a time, turning occasionally until well browned, about 2 to 3 minutes. Remove from oil and drain on paper towels. Cool a few minutes, then transfer to wire rack. Drizzle with Apple Cider Glaze OR using tongs, dunk the doughnuts in the glaze. Serve warm.
To make Apple Cider Glaze, boil apple cider in a small saucepan until reduced in half, about 7 to 10 minutes. Place powdered sugar in medium bowl. Whisk in hot cider and corn syrup until smooth.
NOTE: Doughnuts can also be baked. Simply preheat your oven to 375°F, and bake the risen doughnuts for 8 to 10 minutes.