Feed your sourdough starter and let it become bubbly and doubled in size before mixing.
In the bowl of a stand mixer, combine active starter, milk, eggs, flour, sugar, and salt. Mix on low speed until a rough dough forms.
Gradually add softened butter, a few cubes at a time, while kneading on medium speed. Continue until the dough is smooth, glossy, and passes the windowpane test. Add ons should be added in this stage
Transfer the dough to a greased bowl. Cover and let rise at room temperature for 4β5 hours, or until slightly puffy.
Cover tightly and refrigerate overnight (8β12 hours) for deeper flavor and easier handling.
In the morning, remove dough from the fridge and divide into 8 equal pieces (about 133 g each). Shape each into a smooth, tight ball.
Place the dough balls into a greased and parchment-lined 9-inch springform or cake pan. They should fit snugly but not be squished.
Cover the pan loosely and place it in a warm, humid spot to rise.π Tip: Put the covered pan in your turned-off oven with a cup of boiling water on the bottom rack.Let the rolls proof until puffy, slightly jiggly, and nearly doubled in size β this may take 4β6 hours depending on temperature. Once the rolls are proofed, preheat your oven to 375Β°F (190Β°C).
In a small bowl, whisk together 1 egg and 1 tablespoon of milk. Gently brush the tops of the rolls.
Bake for 25β28 minutes, or until the tops are deep golden brown. Tent with foil halfway if browning too quickly.
Remove from the oven and immediately brush the tops with melted butter for shine and softness. Let cool 15 minutes before releasing the pan latch and serving