Roast the apples: Preheat oven to 350Peel and core the apples and cut into thin wedges. Line a baking sheet with parchment paper. Scatter apple slices evenly on pan. Sprinkle with about 1/4 tsp of cinnamon. Roast in preheated oven for 15 minutes. Remove from oven and allow to cool on the baking sheet until completely cool.
Make the bread dough: Stir together 2 cups of the flour, 1/4 cup sugar, the yeast and salt in a large bowl or the bowl of a stand mixer fitted with a paddle attachment.
In a small saucepan, heat the milk and butter over low heat just until the butter is melted. Alternately, warm in the microwave for about 45 seconds. Remove from the heat and add the 1/4 cup water. Set aside until cooled to just warm (120 to 130°F for instant yeast or about 110F for active dry yeast), about 1 minute. Stir in the vanilla.
Add the milk mixture to the flour mixture and, using a rubber spatula or the paddle attachment, mix until the dry ingredients are evenly moistened. With the mixer on low speed, add the eggs, one at a time, mixing just until incorporated after each addition. Stop the mixer and add the remaining 1/2 cup flour.
If using a stand mixture, remove the paddle attachment and place the kneading hook on the mixture. Resume mixing on low speed, adding additional flour as needed to make a smooth, moist and just slightly sticky dough. If making by hand, knead with as little additional flour as needed until dough is smooth.
Place the dough in a large, greased bowl, cover tightly with plastic wrap and let rise in a warm place until doubled in size, about 45 to 60 minutes.
Make the cinnamon sugar filling: While the dough is rising, in a small bowl, mix together the white sugar and cinnamon. Set aside.
Assemble the pull apart bread: Preheat the oven to 350°F with the rack in the centre of the oven. Spray a 4 x 10-inch tea loaf pan with cooking spray. **Alternately, use a 9x5-inch loaf pan and see Notes at bottom for cutting strips. Set on to a baking sheet and set aside.
Place risen dough on a lightly floured surface and gently deflate the dough. Roll the dough into a 12-inch by 21-inch rectangle. Using a sharp knife and with the long side closest to you, cut the dough into 6 strips even strips about 3 1/2 inches wide, making 6 strips 3 1/2-inches wide and 12 inches long. Using a pastry brush, brush the 4 Tbsp melted butter generously over each of the strips of dough. Scatter all the cinnamon/sugar mixture evenly over-top of the strips.
Gently layer all the strips on top of each other into one pile. Your pile will be 12 inches long and 3 1/2 inches wide. Use a ruler to mark 2-inch increments along the 12-inch side. Using a sharp knife, cut the pile into 6 even pieces, cutting at each 2 inch increment mark, making 6 separate piles about 3 1/2 x 2 inches in size. Arrange the piles in a row in your prepared loaf pan by standing them up in a row along the pan (you may need to push them together gently, to fit them all in). Scatter any cinnamon sugar the was left behind on your work surface over-top of the loaf.
Gently slide cooled, roasted apple slices in between the dough slices here and there across the loaf, trying to get one slice of apple between each layer of dough and alternating from one side to the other (so the slices aren't all in the middle or in on one side). Don't push them down completely. Leave the top edge of the apple slice just peeking out the top. You may not need quite all of the apples you roasted.
Cover the pan with plastic wrap and let the dough rise in a warm place until puffy and almost doubled in size, 30 to 60 minutes.
Bake the loaf on top of a baking sheet, until golden brown and they sound hollow when tapped, about 35 minutes or until it reaches about 190-195F when tested with an instant read thermometer. If the top seems to be at risk of over-browning, cover the top loosely with a sheet of aluminum foil and continue cooking.
Remove from oven and allow to cool in the pan for 15 minutes, then run a knife around the edge and remove loaf to a cooling rack set on top of a baking sheet. Allow to cool completely.
Make the glaze: In a medium bowl combine the icing sugar with the milk and vanilla until the mixture is smooth and pours easily off a spoon. *You may need to add a touch more milk. Brush the glaze over the top of the cooled loaf.