• Mix the sourdough starter, milk, eggs, sugar, salt and flour in a large mixing bowl or in the bowl of a stand mixer. Knead with dough hook attachment on medium speed until smooth.
• Gradually add softened butter and continue kneading until fully incorporated. If the dough seems to stick to the sides of the bowl, mix in another ¼ cup of flour and keep mixing until smooth.
• Cover and let the dough rise at room temperature for 6-8 hours, or until it doubles in size. Rise time will vary depending on strength of starter and room temperature.
• Mix filling spread ingredients in a small bowl.
• Roll out the dough into a rectangle with a rolling pin on a lightly floured work surface.
• Spread softened butter spread over the top of the dough.
• Roll the dough tightly into a log and cut into even slices with either unflavored dental floss, or a sharp knife using light hand and knife pressure.
• Arrange the rolls in a greased baking dish like a 9x13 cake pan, leaving space for them to expand. Cover and place in a warm place for their second rise, which should take 3-5 hours. You can also put them in the fridge overnight at this point and bake the next morning.
• Preheat the oven to 375°F (190°C).
• Bake the rolls for 20-25 minutes.
• Remove from oven and let cool slightly before adding caramel glaze (instructions for caramel are below).
• Top with caramel glaze and serve warm. After 24 hours, rewarm rolls in microwave to soften.

Caramel Glaze Instructions:

• In a small saucepan over low-medium heat, melt a stick of butter together with a cup of brown sugar.
• When the sugar has dissolved, mix in ¼ cup of heavy cream.
• Let simmer for a few minutes then remove from heat, and add vanilla and salt.
• Let it cool down for 10 minutes and then whisk in ½ cup powdered sugar. This turns it into a caramel-glaze.
• When the cinnamon rolls have cooled for about 15 minutes, drizzle the caramel glaze over them.