1large honeycrisp applepeeled, cored, and shredded
4 ½cupsground walnuts
In a mixing bowl of a stand mixer, pour the milk and sprinkle the yeast on top. Let it proof for 5 to 10 minutes until foamy.
Add the sugar, salt, and butter to the mixing bowl. Turn on the stand mixer that's been fitted with a dough hook and beat until combined.
Add 3 cups of flour and mix until smooth.
Slowly add the remaining flour, scraping down the sides as needed, until the flour is completely combined. Continue to beat for 4 to 5 additional minutes to knead the dough.
Oil a large mixing bowl and place the dough in the bowl. Turn and flip the dough so it's coated with oil.
Loosely cover the plastic wrap and place in a warm area until doubled, about 1 hour.
Place the sugar, butter, salt, cinnamon, and egg into a medium saucepan over low heat. Stir the mixture until the butter is completely melted and the mixture has thickened enough to coat the back of a wooden spoon.
Stir in the walnuts and shredded apple and remove from the heat. Allow to cool to room temperature.
Line a large rimmed baking sheet (or two if using a smaller baking sheet) with parchment paper. Lightly coat with nonstick baking spray.
Punch the dough down and divide into four equal pieces.
On a lightly floured surface, roll out each piece of dough into a 12 x 20 inch rectangle.
Spread a quarter of the filling across the dough, leaving ½ inch on all sides.
Roll the dough up from the longest side like a cinnamon roll or jelly roll. Pinch the edge into the roll to seal the seam and pinch the ends to seal them. Make sure the seam side is down and gently tuck the pinched ends under the roll.
Carefully transfer the roll to the baking sheet, placing it with the seam side down.
Repeat rolling the dough, spreading the filling, rolling the nut roll up, and transferring to the baking sheet three more times.
When all four rolls are on the baking sheet, cover loosely and place in a warm area and allow to rise for 30 minutes.
Preheat the oven to 350 degrees F.
Bake the nut rolls for 30 to 40 minutes until golden brown. Remove from the oven and allow to cool on a wire rack.
Add the powdered sugar and milk to a mixing bowl. Whisk to combine until smooth. Add additional milk 1 tablespoon at a time for a thinner consistency.
Spread over the nut rolls or transfer to a piping bag with the corner snipped and drizzle over the nut rolls.