Delicious Easter Brioche

Brioche -

INGREDIENTS FOR THE SPONGE
1 c. all-purpose flour (128 g.)
1 (0.25-oz.) packet or 2 1/4 tsp. active dry yeast (7 g.)
1/2 c. milk, lukewarm (120 g.)

FOR THE DOUGH
6 large eggs, room temperature (320 g.)
3 c. all-purpose flour (384 g.)
1/2 c. granulated sugar (105 g.)
2 tsp. kosher salt (12 g.)
1 c. (2 sticks) butter, softened, plus more for pans (227 g.)

FOR THE EGG WASH
1 large egg
1 tbsp. water
Kosher or sea salt, for sprinkling

1. Make the sponge: To the bowl of a stand mixer fitted with the hook attachment, add 1 cup flour, yeast, and milk. Using a spatula, mix until well combined, then cover with plastic wrap and let sit for 45 minutes.
2. Once the sponge has formed some air pockets, add in eggs, remaining 3 cups flour, sugar, and salt. Mix on medium speed until well combined, then gradually increase to medium-high speed and continue mixing until dough pulls away from the sides of the bowl and becomes shiny and elastic, scraping down bowl every 4 to 5 minutes, 10 to 13 minutes.
3. With the mixer running, add in butter gradually, 1 tablespoon at a time, letting each tablespoon fully incorporate into the dough before adding the next, 13 to 15 minutes. Continue mixing on medium-high speed for 5 to 7 minutes until the dough passes the windowpane test. Cover bowl with plastic wrap and let rest about 1 hour or doubled in size.
4. To bake next day: Once dough has doubled in size, punch down to deflate dough completely, then re-cover with plastic wrap. Refrigerate overnight until you are ready to bake the next day. Follow instructions in the next step, letting dough proof until doubled before baking, longer if needed, up to 2 hours 30 minutes.
5. To bake same day: Once dough has doubled in size, turn out onto a floured surface and punch down dough. Divide in half using a bench scraper. Cut each half into six equal pieces. Flatten each piece into a rectangle, then fold short ends in towards each other as if folding a letter. Flatten again and tightly roll into a log starting with the short end. Repeat with all pieces.
6. Grease 8”-x-5” loaf pans with butter. Place 6 pieces of dough seam-side down in one straight row into each prepared pan. Cover with plastic wrap.
7. Preheat oven to 375°. Let dough proof until puffy and doubled in size, 1 hour to 1 hour 30 minutes. In a small bowl, whisk together remaining egg and water. Brush egg wash on top of loaf and sprinkle lightly with salt.
8. Bake until deeply golden on top and the center of the loaf registers between 190° and 205°, about 30 minutes.
9. Let cool 5 minutes then turn loaves out onto a cooling rack. Let cool completely before serving.