Cinnamon Swirl Sourdough Braid

1. In a large mixing bowl, combine the flour and salt. In a separate bowl, mix the warm water, sourdough starter, and sugar until well blended. 2. Pour the liquid mixture into the dry ingredients and stir until a shaggy dough forms. 3. Knead the dough on a floured surface for about 10 minutes until smooth and elastic. Place it in a greased bowl, cover with a damp cloth, and let it rise for about 4-6 hours or until doubled in size. 4. Once the dough has risen, punch it down and roll it out into a large rectangle (about 12x18 inches). 5. Brush the melted butter over the dough and sprinkle the brown sugar and cinnamon mixture evenly, followed by adding nuts if using. 6. Starting from one long side, tightly roll the dough into a log and pinch the edges to seal. 7. Place the log seam-side down on a floured surface and braid it by cutting it in half lengthwise and twisting the two halves together. 8. Transfer the braided loaf to a lined baking sheet and cover it with a kitchen towel, allowing it to rise again for about 1-2 hours until puffed up. 9. Preheat the oven to 350°F (175°C). Brush the loaf with the beaten egg for a shiny finish. 10. Bake for 30-35 minutes or until golden brown and sounds hollow when tapped on the bottom. 11. Let the loaf cool on a wire rack before slicing.