Add bread flour (280g) and warm water (210g) to a large bowl. Mix until no dry flour remains. The mixture will be thick but stirrable.

Sprinkle the instant yeast over the surface and stir until evenly distributed.

Use plastic wrap or a damp towel. The sponge needs room to expand.

Leave at warm room temperature (78-82°F) for 3-5 hours. Ready when doubled, domed, bubbly, and smells yeasty.

Scrape all of the sponge into the bowl of a stand mixer fitted with the dough hook.

Add fresh bread flour (280g), room temperature milk (115g), softened butter (45g), sugar (35g), salt (10g), and instant yeast (3g).

Mix on low speed (speed 2) for 3 minutes until everything comes together into a rough dough.

Increase to medium speed (speed 4) and mix for 6-8 minutes until smooth and passes the windowpane test.

Transfer dough to a lightly oiled bowl. Cover with plastic wrap.

Ferment at warm room temperature (78-82°F) until doubled in size, about 1-1.5 hours.

Press gently with a floured finger. If the indent springs back slowly, it's ready.

Turn onto a lightly floured surface. Divide into two equal pieces (approximately 530g each).

Gently pat each piece into a rough rectangle, then fold in thirds like a letter. Flip seam-side down.

Cover loosely and rest 10 minutes to relax the gluten.

Lightly butter or spray two 9x5 inch loaf pans.

Flip dough seam-side up. Press or roll into a rectangle about 8 inches wide by 12 inches long.

Starting from a short end, roll the dough tightly toward you, creating a log. Pinch the seam to seal.

Pinch ends and tuck under. Place seam-side down in prepared pans. Dough should fill about half the pan.

Cover loosely with plastic wrap or a damp towel.

Proof at warm room temperature until dough crowns about 1 inch above the rim of the pan (45-60 minutes).

Poke gently with a floured finger. Indent should spring back slowly and mostly fill in. Don't over-proof.

Lightly butter or spray two 9x5 inch loaf pans.

Flip dough seam-side up. Press or roll into an 8x12 inch rectangle.

Starting from short end, roll toward you into a tight log. Pinch seam to seal.

Pinch ends and tuck under. Place seam-down in pans—dough should fill about half.

Preheat oven to 375°F (190°C) during last 20 minutes of proofing.

Beat egg with water and brush gently over tops for a golden, glossy crust.

Place pans on middle rack with space between. Bake 30-35 minutes until deep golden brown.

Internal temperature should reach 195-200°F. If tops brown too quickly, tent with foil at 25 minutes.

Rest in pans 5 minutes. Turn out onto wire rack. Cool completely before slicing—at least 1 hour.