4tablespoonsunsalted butter, at room temperature, divided
For The White Chocolate Ganache:
4oz. (115g)white chocolate, chopped
To the bowl of a stand mixer fitted with the paddle attachment, combine 1 cup of flour, yeast, sugar and salt. Set aside. Heat the milk at a low power in the microwave until it's lukewarm to the touch (about 120-130 F degrees). Add the warm milk, butter, egg and vanilla to the flour mixture and mix at low speed until all ingredients are combined, scraping sides of bowl frequently. With a wooden spoon, stir in the remaining flour, 1/3 cup at a time until the dough begins to leave the sides of the bowl. Don't over-flour the dough - it shouldn't be sticky, but should be soft.
Now, place your dough on a lightly floured surface and knead it with your hands until it is smooth, elastic and springs back when pressed (about 5 minutes). Form the dough into a ball and transfer it to a lightly greased bowl. Cover with plastic-wrap and let sit in a warm place for about 1.5 hours, or until it doubles in size.
As the dough is rising, melt 2 tablespoons of butter in a saucepan. Add the apple slices and saute until soft, for about 5 minutes. Drain the apples and set aside to cool. In a small bowl, mix together brown sugar, chopped walnuts and cinnamon.
Grease and line a 9x13 inch baking dish with parchment paper. After dough has doubled in size, place it onto a lightly floured surface and begin to roll it into a 13x10 inch rectangle. Butter the dough with 2 tablespoons of softened butter and sprinkle with a half of the brown sugar mixture. Then spread the apples on top and sprinkle with the remaining brown sugar mixture. Roll the dough up tightly beginning at the short side and seal well by pinching edges of roll together.
With a very sharp knife or dental floss cut the roll into 1-inch thick slices and arrange them in the prepared baking dish. Rolls shouldn't touch each other. Cover with plastic wrap and let them rise in a warm place for about 20-30 minutes.
Preheat the oven to 350 F degrees. Bake the rolls for about 20 to 25 minutes, or until slightly golden-brown on top.
White Chocolate Ganache:
While rolls are baking, prepare the glaze. Microwave chopped chocolate in 15-second intervals until chocolate is almost melted. Stir to fully melt and set aside. In a small saucepan, heat heavy cream until just about boiling, stirring constantly. Remove from the heat, pour hot cream over chocolate and stir to blend well. Using the electric mixer, beat the chocolate mixture for several seconds.
Once the rolls are baked, allow them to cool for about 5 minutes. Drizzle the chocolate ganache over the rolls and serve. Enjoy!
Leftover rolls can be heated for a few seconds in the microwave before serving.