For the filling:
2 tablespoons unsalted butter
1/2 cup packed brown sugar
1 tablespoon ground cinnamon
1/2 teaspoon vanilla extract
3 medium apples (about 2 cups), peeled, cored, and thinly sliced
1/2 cup pecans or walnuts, chopped (optional)
For the dough:
1/4 cup (4 tablespoons) unsalted butter, melted
1/3 cup lukewarm milk
1/4 cup lukewarm water
2 large eggs
1 teaspoon vanilla extract
3 cups King Arthur Unbleached All-Purpose Flour
1/4 cup sugar
1/2 teaspoon salt
2 1/4 teaspoons instant yeast
For the glaze:
1 cup powdered sugar
1 tablespoon milk
mix both ingredients together in a small bowl. Add more milk if necessary to get desired consistency. I like it to be the consistency of a thick syrup.
To make the dough:
Whisk together the butter, milk, water, eggs, and vanilla extract.
In the bowl mixer, mix together the flour, sugar, salt, and yeast, then add the wet ingredients. Using the dough hook attachment mix and knead, until the dough is smooth. The dough will be quite soft. If it seems too dry add a little water, if it seems too sticky add just a little flour, up to a 1/4 cup.
Place the dough in a lightly greased bowl, cover, and allow to rest until doubled in size, about 1 hour.
Grease a 9" x 5" loaf pan.
Gently deflate the dough and turn it out onto a lightly greased surface.* Roll the dough into a 12" x 20" rectangle.
Stir the vanilla into the melted butter. Spread the butter mixture over the entire top on the dough. Sprinkle the brown sugar over the top, using your hand to spread it evenly over the butter. Sprinkle the cinnamon evenly over the dough. Add the apples next, evenly on top of the cinnamon and sugar and sprinkle the nut over top, if using.
Cut the dough crosswise into six 3 1/2" x 12" strips. Stack the strips on top of one another. Cut the stack into six pieces, about 2" x 3 1/2" each. This part is a little messy but it doesn't have to be perfect.
Turn the pieces on edge, and place them in the loaf pan one in front of the other from one end of the pan to the other, squeezing them in tight. I sprinkled any nuts or apples that had fallen off over the top of the dough after I put it into the pan.
Cover the pan and allow the loaf to rise for 30 to 60 minutes, until it's almost doubled in size. While the loaf is rising, preheat the oven to 350°F.
Bake the loaf for 45 to 55 minutes in the center of the oven, tenting it with foil after 30 minutes. Remove the loaf from the oven, and transfer it to a rack to cool for 15 to 20 minutes before turning it out of the pan to cool completely.
While still slightly warm, spoon the glaze over the top of the bread.