In a large bowl, whisk together the active sourdough starter and milk until fully dissolved. Add the sugar and room-temperature egg, whisking until smooth.

Sift in the flour and salt, stirring until a shaggy dough forms. Add the room-temperature butter and mix until fully incorporated.

Tip: Your butter should be soft enough that you can easily press your finger through it. Cold butter will fight you here.

Cover the bowl with a damp cloth and let the dough rest for 20 minutes. This allows the flour to fully hydrate.

After resting, knead the dough:

Stand mixer: Medium speed with a dough hook for about 12 minutes

By hand: Knead for roughly the same amount of time

The dough should become smooth and pull away from the sides of the bowl.

Cover the bowl and let the dough ferment at about 71°F (21°C) for 8–10 hours, or overnight, until doubled in size.

Temperature matters here — cooler homes may need more time, warmer homes slightly less.

In a small saucepan, melt the butter over medium heat. Continue cooking, stirring constantly, until it turns golden brown and smells nutty — about 5 minutes.

Remove from heat and combine the brown butter with brown sugar, cinnamon, salt, and flour in a small bowl. Set aside.

Lightly flour your work surface. Gently shape the dough into a square, then roll it into a 16″ x 16″ rectangle.

Spread the brown butter filling evenly over the dough, leaving a one-inch margin along one edge to help seal the roll.

Roll the dough tightly into a log, starting from the opposite edge. Lightly wet the margin before sealing and let it rest seam-side down.

Using a sharp, non-serrated knife, cut the log into 12 equal rolls. Wetting your knife every few cuts helps prevent dragging and tearing.

Arrange the rolls in a greased 9″ x 13″ pan, evenly spaced.

Cover the pan and let the rolls rise at about 71°F (21°C) for 1–2 hours, until visibly puffy and touching.

If your kitchen is cool, this step may take longer — patience pays off here.

Preheat your oven to 350°F (177°C).

Bake the rolls on the center rack for 25–30 minutes, until lightly golden and cooked through.

While the rolls bake, brown the butter for the frosting using the same method as before.

In a bowl, combine the hot brown butter with cold cream cheese, mashing with a fork until mostly smooth. Add powdered sugar, vanilla, and milk, mixing until creamy and velvety.

Let the rolls cool for about 15 minutes, then generously spread the frosting over the warm rolls.

Serve immediately — preferably with coffee, pajamas, and no plans.