Combine water, sugar, and yeast in a bowl. Let sit until foamy, approx. 5-10 min. If mixture does not foam, the yeast is dead and should be tossed.
In your mixer bowl, add the bread flour, salt, sourdough starter (see recipe), and yeast mixture with a dough hook attachment.
Mix on low speed until dough comes together.
Once dough forms, turn up the speed by one and continue to knead until dough is smooth and springy. Dough should bounce back when poked.
Shape Dough into a nice round ball and spray with oil. Cover with plastic and let rest in a warm spot until doubled in size, approx. 1-2 hours (depending on how warm the area is).
Punch down dough and scrape out of bowl onto a lightly floured surface.
Divide dough into 3 pieces, approx 270g each
Roll each piece into a smooth round ball. Place on prepared baking pan lined with parchment paper.
Preheat oven to 425°F with a baking pan filled with 1 cup of water on the bottom of the oven floor. Make sure you have a racking the middle of the oven set for the bread, and spray bottle of water ready.
Cover dough with wet paper tools and let rise until doubled in size. Checking after 30 min, you want the oudhg to be airy and springy. Continue proofing dough (letting it rise) if the dough still feels tight (not enough air). Do not let it go to the point where it collapses when touches - this means it's over proofed.
Whisk the egg with a little bit of water and brush the tops of the dough with the egg wash.
Cut a slit on top of the dough with a sharp knife
When inserting tray of bread into the oven, spray the tops of the bread and sides of the oven with water. Work quickly to keep oven temperature from dropping.
Bake for 2 minutes and quickly spray the bread and oven walls again.
Bake for another 15-20 minutes, turning tray halfway through. Bake until bread is nice and brown.
Day 1: Combine 6 tbsp (57g) flour and 1/4 cup (57g) water until smooth. Cover loosely with plastic or a kitchen towel. Let sit at room temperature for 24 hours.
Day 2: Add another 6 tbsp (57g) flour and 1/4 cup (57g) water until smooth. Cover loosely with plastic or a kitchen towel. Let sit at room temperature for 24 hours.
Repeat step 2 every day until you have fed the started 5 days in a row.
Starter will be ready to use after 5th day. It should be bubbly and smell sour.
If you will be using your starter after the 5 days, continue feeding it daily. Throw away less than half of the starter before feeding it if you need to reduce it in size.
For long term storage, feed the starter with double the amount of flour to water, and store in the fridge. Be sure to keep the starter fully covered, as it has more of a chance of drying out in the fridge. Feed once a week when storing in the fridge.