In a large bowl, whisk warm milk, sugar, and starter. Add egg and the 4 tbsp melted butter, then stir in flour and salt until a shaggy dough forms.

Knead on a lightly floured surface for 8 to 10 minutes until smooth and elastic.

Place in a buttered bowl, cover, and let rise until doubled, about 4 to 5 hours.

Punch down dough, roll into a 12x8-inch rectangle. Brush with about 2 tbsp melted butter, cut into 4 strips lengthwise, stack, then cut crosswise into 6 pieces. Arrange cut-side down in a buttered 9x5-inch loaf pan.

Cover and let rise until puffed about an inch above the pan rim, 1.5 to 2 hours. Preheat oven to 350°F (180°C) during the last 20 minutes.

Bake 25 to 30 minutes until deep golden and internal temp reads 200-205°F (93-96°C). Cool in pan 5 minutes, turn out, brush with remaining melted butter, and serve warm.