1. Heat the butter and milk in a small saucepan on the stove or in a small bowl in the microwave until 110 degrees F, but no hotter. If the liquid is hotter than 120 degrees F, it can kill the sourdough starter.
   57 grams unsalted butter, 240 grams milk
2. Meanwhile, add the bubbly sourdough starter, room temperature egg, and sugar to the bowl of a stand mixer with a paddle attachment. Mix on low speed until combined, then gradually add the warm milk and melted butter.

   You can also mix the dough by hand if you're not using a stand mixer.
   100 grams active sourdough starter, 1 egg, 50 grams sugar
3. To the wet ingredients, add the flour and salt and mix again on low speed. Stop to scrape the sides of the bowl to incorporate all the dry ingredients and then continue to mix on low for 1-2 minutes. 
   450 grams bread flour, 9 grams salt
4. The dough will look thick and sticky, like a batter. Cover with plastic wrap or and allow the dough to rest for 30 minutes.

Knead

1. After 30 minutes, remove the cover and knead the dough with the dough hook attachment at medium speed for 10 - 15 minutes. 

   This can be done by hand. Knead the dough for the same amount of time, or until the dough passes the windowpane test.

   Note: You'll know the dough has been kneaded when it is smooth and shiny. The dough will completely pull away from the sides of the bowl when it is being kneaded and it will pass the windowpane test. If you notice that the dough is still too sticky, you might need to add a touch more flour. I would add 15 grams (1 Tablespoon) of flour at a time until the dough feels tacky to the touch.
Windowpane Test means when you stretch a small section of dough into a thin film, the light can pass through without the dough tearing. If this is accomplished, the dough has been properly kneaded.
2. Remove the dough and place it in a lightly greased straight-edge bowl. I like to use butter or olive oil. Cover it again.

   I love using this straight-edge bowl because it allows me to clearly see when my dough is done rising.

Bulk Fermentation

1. Place the dough in a warm place in your kitchen to double in size.

   In my 70 degree F kitchen, the first bulk rise takes about 7-8 hours. The bulk fermentation time greatly depends on the temperature of your kitchen. If you have a colder kitchen, the rise time will take longer. If your kitchen runs warm, the first rise will take less time.

Cold Proof:

1. If your dough has doubled in size, but you are wanting to bake it following morning, place the dough, covered, in the fridge overnight. If your dough has doubled in size and you are ready to bake, skip this step and continue on to shaping.

Shape

1. Just before the bulk fermentation is complete, grease a 10-inch bundt pan with butter. Set aside.

   If you do not have a bundt pan, you could also use a greased 9x13 baking dish or 9x5 loaf pan. 

   Note: If you cold proofed the dough, remove it from the fridge.
2. Once the dough has doubled in size, punch the top of the dough to remove all the air bubbles, then, place the dough on a clean work surface. Gently stretch the dough into a large rectangle shape. With a bench knife or sharp knife, cut the dough into bite-sized pieces. 
3. In one bowl, add the melted butter and a pinch of salt and in a separate bowl, mix the cinnamon and sugar until combined. Taking a few pieces of dough at a time, dip them first in the melted butter and then in the cinnamon sugar before placing them in the prepared bundt pan.

   Don’t overthink this - it isn’t Tetris, just continue to evenly disperse the pieces in the bundt pan. They will stick together when baked.
   6 grams cinnamon, 113 grams unsalted butter, melted, pinch of salt, 200 grams sugar
4. Repeat with the remaining pieces of dough. 

Second Rise

1. Cover the bundt pan with plastic wrap and leave in a warm place until the pieces of dough have puffed up.

   In my 70 degree F kitchen this took about 2-3 hours. If your kitchen is cooler, this will take longer. If your kitchen is warmer, this will take less time. 

   Note: If you cold proofed your dough overnight in the fridge, the dough will be cold and will take longer to return to room temperature and complete its second rise. I placed my covered bundt pan in my oven on the “Proof” setting, which was about 90 degrees F. It took about 1-2 hours for it to puff up. If your oven doesn’t have the proof setting, you could put the dough in an OFF oven with the oven light on. DO NOT rush this step. The dough should looks puffed up and not be cold to the touch. If you rush this step, the dough will bake up dense.

Bake

1. Once the dough has risen (it shouldn’t be cold at all and when you poke the dough, your finger print should slowly rise), preheat the oven to 350 degrees F and prepare the butterscotch. 
2. Add the brown sugar, butter, salt and vanilla in a small saucepan at medium-high heat. Stir occasionally until the butter has completely melted and the ingredients are fully incorporated. Constantly stir as you let it continue to cook and bubble for 1 minute before removing from the heat. Evenly pour the butterscotch on top of the dough. 
   110 grams light brown sugar, 57 grams unsalted butter, 1 gram salt, 4 grams vanilla extract
3. Bake the Sourdough Monkey Bread for 30-35 minutes or until the internal temperature has reached 190-200 degrees F.

Cool

1. Keep the monkey bread in the bundt pan for at least 10-15 minutes to allow the butterscotch to cool slightly. This will allow it to stick to the dough rather than running off onto the plate.
2. While the monkey bread cools, prepare the vanilla icing. 
3. In a bowl, add the powdered sugar, 15g (1 T) of milk at a time until the desired consistency is reached. Add the vanilla and whisk until smooth. 
   130 grams powdered sugar, 45 grams milk, 2 grams vanilla extract
4. To remove, place a plate on top of the bundt pan and then flip the pan upside down. Drizzle the icing on top and serve warm. Enjoy!