In the bowl of a stand mixer, combine the active sourdough starter, bread flour, sugar, warm water, salt, and melted coconut oil. Mix until the dough forms a rough ball, then knead on medium-high for about 5 minutes. The dough should start to pull away from the sides of the bowl.
Remove and shape the dough into a ball. Place it in a greased large bowl, cover tightly with plastic wrap, and set in a warm place for the first rise—about 8-12 hours, or until doubled in size.
After double in size, prepare the caramel sauce. In a small saucepan, melt butter and whisk in the brown sugar until dissolved. Remove from heat and stir in heavy cream. Pour half of the mixture into a greased bundt pan and set aside the rest to top the dough later.
Turn the risen dough onto a lightly floured surface. Divide the dough until you have 32-40 small pieces. A bench scraper or sharp knife makes this easy. (Each ball should weigh about 20 grams; the total dough weight is approx. 838 grams.)
Shape each piece into a tight ball by pulling the edges inward and pinching them together.
In a shallow dish, melt the 6 tablespoons of butter. In a separate bowl, mix sugar and cinnamon.
Roll each dough ball in melted butter, then in the cinnamon sugar mixture, and layer them into the prepared bundt pan. Pour the remaining caramel topping over the top.
Cover with plastic wrap and let rise for a second rise of about 2 hours, or until puffy.
After puffy, preheat oven to 350 F.
Bake in the preheated oven for 40 minutes. At around the 20-minute mark, tent loosely with foil to prevent over-browning to the exposed dough.
The monkey bread should be golden and bubbly. You can use a thermometer to check the internal temperature—look for around 190°F.
Let cool in the pan for about 15 minutes before inverting onto a serving platter. Note: some of the caramel may run off and pool; if you prefer a cleaner presentation, allow the bread to cool longer in the pan. You can also cut the caramel ingredients in half and have less caramel sauce.