Warm whole milk until lukewarm. In a bowl or stand mixer, combine warm milk, sourdough starter, and cane sugar. Stir gently.

Add room temperature egg and mix well.

Gradually incorporate bread flour and sea salt until no dry spots remain. Knead by hand or with a mixer for about 8 minutes until smooth and elastic.

Cover and let rise at room temperature until doubled in size, about 4 hours.

Roll out dough into a rectangle; spread melted butter and sprinkle with cocoa powder and chocolate chips.

Roll tightly and cut into slices; place in a greased baking dish.

Let rise again for about an hour until puffed up.

Preheat oven to 350°F (175°C). Bake for 25-30 minutes until golden brown.

Prepare glaze by mixing milk, cocoa powder, powdered sugar, and vanilla; drizzle over rolls while warm.