Poolish: 150 g bread flour (1 1/4 cups), 150 g water (2/3 cup), 1/8 tsp instant yeast
Dough: 350 g bread flour (2 3/4 cups)
200 g cool water (3/4 cup + 2 tbsp)
10 g fine salt (1 3/4 tsp)
3 g instant yeast (1 tsp)
Semolina or rice flour for the couche or towel
1 tbsp black sesame seeds per baguette (optional, for a sesame baguette)
How to make it
Poolish (5 min, then 12 to 16 hr): Stir the poolish ingredients into a wet paste, cover and leave at room temperature overnight until bubbly and domed.
Mix (10 min): Add the water to the poolish and loosen it, then add flour, salt and yeast. Mix and knead 5 minutes by hand (or 4 minutes in a mixer) until smooth.
Bulk (2 hr): Cover and rise 2 hours, folding the dough over itself at 30, 60 and 90 minutes.
Divide and pre-shape (5 min plus 25 min): Cut into three pieces and fold each loosely into a short log. Rest 25 minutes under a towel.
Shape (10 min): Pat a log flat, fold the top third down and seal with the heel of your hand, then fold in half lengthwise and seal the seam. Roll it under your palms from the middle out to about 35 cm (14 in), with pointy ends. Roll in sesame seeds now if using.
Proof (45 min): Lay seam-side up in a floured couche or pleated towel. Cover and proof 45 minutes, until puffy and a fingertip dent springs back slowly.
Bake with steam (22 to 25 min): Heat the oven to 250C (480F) with a baking stone or upturned tray, and a metal pan on the bottom shelf. Flip the baguettes onto parchment, score three or four long, overlapping slashes almost parallel to the length. Slide them onto the stone and pour a cup of boiling water into the pan for steam. Bake 22 to 25 minutes until deep golden. They should crackle as they cool.
Tips
Steam in the first 10 minutes gives the shiny, crackly crust.
Score at a very shallow angle, like peeling the skin back, not straight down.