In the early evening, mix 40 g water, 20 g sourdough starter, 20 g sugar, and 80 g bread flour in a glass jar. Knead outside of the jar to fully incorporate the ingredients. Cover loosely and let ferment in a warm place until morning.

In the morning, set out 56 g unsalted butter to soften. Put your two eggs in a bowl of warm water to quickly bring them to room temperature.

To make the tangzhong, whisk together 18 g bread flour and 88 g whole milk. Microwave in 20-second intervals until thickened and reaches 150°F (65°C), about 2-3 rounds total. Pop it in the fridge for 5-10 minutes, or until it has cooled down to room temperature.

If mixing by hand: In a glass mixing bowl, warm 85 g milk to about 90°F/32°C. Add 1 egg, 1 egg yolk, and 50 g sugar. Then, add All of the stiff sweet starter, All of the tangzhong, 270 g bread flour, 11 g milk powder (optional), and 7 g sea salt. Knead the dough until fully combined, about 3 minutes. Cover and let rest for 30 minutes.

If using a stand mixer: Add all ingredients to your stand mixer, except for the butter. Mix on low speed for about 10 minutes. Cover and let rest for 30 minutes.

Spread all of your softened butter on top of the dough. Pinch and squeeze the butter into the dough until it's mostly incorporated. Cover and let rest for 30 minutes.

Strengthen the dough for 2-3 minutes via stretch and folds, kneading, or slap and folds.

First rise: Place your bowl in a warm spot for 3-5 hours, or until the dough has relaxed and is showing signs of fermentation.

Dump out the dough and weigh it. Divide the total weight by 24. Shape the pieces into taut balls and place them into a greased 9x13 baking dish. Cover with plastic wrap and let rise until the rolls are touching each other.

Preheat oven to 400°F (205°C). Whisk together 1 egg with 8 g powdered sugar. Brush on top of the rolls and bake for 12 minutes. Lower the oven temperature to 350°F (175°C) and bake for an additional 5-15 minutes, or until golden brown.

In a small bowl, combine 8 g butter, melted with 8 g powdered sugar. Brush baked rolls with the mixture. Let cool for about 10 minutes; then, turn out onto a cooling rack.