1. In a large bowl whisk warm milk, sugar, melted butter, and sourdough discard until smooth.

2. Sprinkle in yeast and let sit 5 minutes until bubbly.

3. Add flour and salt and mix until a shaggy dough forms.

4. Knead dough on a floured surface for 8–10 minutes until elastic, or mix in a stand mixer for 5–6 minutes.

5. Place dough in an oiled bowl, cover, and rise 60–90 minutes until doubled.

6. Stir brown sugar and cinnamon in a small bowl and soften butter for the filling.

7. Punch down risen dough and roll into a 10×15-inch rectangle.

8. Spread soft butter over the dough and sprinkle cinnamon sugar and any optional add ins evenly.

9. Roll dough tightly from the short edge, pinch seam closed, and place seam-side down in a greased loaf pan.

10. Cover and proof 45–60 minutes until dough crowns above pan.

11. Preheat oven to 350°F (175°C) and brush loaf with egg wash if using.

12. Bake 35–40 minutes until golden and internal temperature reaches 190°F (88°C).

13. Cool in pan 10 minutes, then transfer to a rack and cool completely before slicing.