• Melt 8 tablespoons (1 stick) of butter in a medium saucepan over medium heat, stirring frequently. Remove from heat.
• Stir in the brown sugar, salt, vanilla extract, and milk until smooth.
• Add the butter mixture to the bowl of a stand mixer along with the flour and sourdough starter. Use dough hook attachment to mix until on low speed until a shaggy dough forms. Cover the bowl with plastic wrap and let rest for 30 minutes.
• Remove the plastic wrap and knead the dough with the dough hook attachment on low speed for 5-7 minutes or until the dough comes together and pulls away from the sides of the bowl.
• Transfer the dough to a lightly oiled bowl and cover with plastic wrap. Let rise for 2 hours.

Make the Filling

• Make the filling by microwaving 4 tablespoons butter for 15-20 seconds. Add the 1½ tablespoons cinnamon and ⅔ cup brown sugar. Stir until fully combined.

Make the Topping

• Melt butter in microwave for about 30 seconds in a small bowl. Add topping ingredients (brown sugar, maple syrup, salt, vanilla extract) except for the pecans, and mix until smooth.
• Use a wooden spoon or rubber spatula to spread the topping evenly in a 9x13 inch baking pan. Sprinkle the pecans evenly over the topping.

Roll Out the Sticky Bun Dough and Fill

• Transfer the dough to a lightly floured surface. Use a rolling pin to roll the dough in an approximate 12x21 inch (32.5x53 cm) rectangle. Try to make the corners as sharp as possible and feel free to use your hands if needed to shape the rectangle.
• Spread the filling evenly over the dough with a spoon. You may need to work the filling a bit by gently scraping up thicker areas and transferring it to areas with less filling.
• Somewhat loosely roll the long edge of dough towards you, forming a long cylinder.
• Use a sharp kitchen knife or unflavored dental floss to cut the rolls into 12 evenly sized rolls.
• Transfer the rolls to the prepared baking pan, placing the rolls on top of the filling and pecans, evenly spaced.
• Cover with plastic wrap and allow to rise at room temperature until the rolls are puffy and starting to touch each other (about 6-8 hours). When the rolls are fully proofed, you can either bake immediately or refrigerate overnight and bake the next day (see baker's schedule above).

When Ready to Bake

• Preheat oven to 350℉.
• Brush rolls with 2 tablespoons milk. Bake in preheated oven for 35-40 minutes if not refrigerated or 40-45 minutes if rolls were refrigerated overnight. When done, the rolls should appear slightly golden on top and reach an internal temperature of 195℉. I highly recommend using a thermometer to check for doneness.
• Allow to cool in pan at room temperature for 15 minutes.
• Place a large baking sheet or serving tray on top of the pan. Flip the buns onto the serving tray and serve warm.