This is a heavenly baguette from "Cook's Illustrated" magazine. It takes about 24 hours, so be sure to start it the day before you want to enjoy it.
Please read entire recipe before beginning!!
For the dough: To sponge, add yeast and all but 2 Tbsp water. Stir briskly with wooden spoon until water is incorporated, about 30 seconds. Stir in flour and continue mixing with wooden spoon until a scrappy ball forms. Turn dough onto countertop and knead by hand, adding drops of water if neccessary, until dry bits are absorbed into dough, about 2 minutes. Dough will feel dry and tough. Stretch dough into rough 8 by 6-inch rectangle, make indentations in dough with fingertips, sprinkle with 1 Tbsp remaining water, fold edges of dough up toward center to encase water, and pinch edges to seal. Knead dough lightly, about 30 seconds (dough will feel slippery as some water escapes but will become increasingly pliant as the water is absorbed). Begin crashing and kneading dough alternately until soft and supple and surface is almost podery smooth, about 7 minutes (to "crash" the dough, fling it vigorously and repeatedly against the countertop). If dough still feels tough and nonpliant, knead in 2 additional teaspoons water.
Test dough to determine if adequately kneaded by performing windowpane test (hold edge of dough and see if it can be stretched into a nearly translucent membrane). If dough tears before stretching thin, knead 5 minutes longer and test again. Gather dough into ball, place in large bowl, and cover with plastic wrap. Let stand 30 minutes, then remove dough from bowl and knead gently to deflate, about 10 seconds; gather into ball, return to bowl, and replace plastic wrap. Let rise until doubled in bulk, about 1.5 hours.
Decompress dough by gently pushing a fist in center of dough toward bottom of bowl. Turn dough onto work surface. With dough scraper, divide dough into two 12-ounce pieces. Working one at a time, with second piece covered with plastic wrap on work surface, cup hands stiffly around dough and drag in short half-circular motions toward edge of counter until dough forms rough torpedo shape with taught rounded surface, about 6.5 inches long. (As you drag the dough, its tackiness will pull on the work surface, causing the top to scroll down and to the back to create a smooth, taught surface.) Repeat with second piece of dough. Drape plastic wrap over dough on work surface; let rest to relax, 15 to 20 minutes.
Meanwhile, line an inverted rimmed baking sheet with parchment paper. Working one at a time, with second piece covered with plastic wrap, roll torpedo seam-side up and press indentation along length of dough with side of outstretched hand. Working along length of dough, press thumb of one hand against dough while folding and rolling upper edge of dough down with other hand to enclose thumb. Repeat folding and rolling 4 or 5 times until upper edge meets lower edge and creates a seam; press seam to seal. Dough will have formed cylinder about 12 inches long. Roll dough cylinder seam-side down; gently and evenly roll and stretch dough until it measures 15 inches long by 2.5 inches wide. Place seam-side down on prepared baking sheet. Drape clean dry kitchen towel over dough and slide baking sheet into large clean garbage bag; seal to close. Refrigerate until dough has risen moderately, at least 12 but no longer than 16 hours.
To bake: Remove one oven rack from oven; adjust second oven rack to lowest position. Place pizza stone on rack in oven and heavy rimmed baking sheet on oven floor. Heat oven to 500°F. Remove baking sheet with baguettes from refrigerator and let baguettes stand covered at room temperature 45 minutes; remove plastic bag and towel to let surface of dough dry, then let stand 15 minutes longer. The dough should have risen to almost double in bulk and feel springy to the touch. Meanwhile, bring 1 cup water to simmer in small saucepan on stovetop.
With a lame or single-edge razor blade, make five 1/4-inch deep diagonal slashes on each baguette. Brush baguette with egg white and mist with water. Working quickly, slide parchment sheet with baguettes off baking sheet and onto hot pizza stone. Pour simmering water onto baking sheet on oven floor and quickly close oven door. Bake, rotating loaves front to back and side to side after 10 minutes, until deep golden brown and an instant-read thermometer inserted into center of bread through bottom crust registers 205 to 210°F, about 5 minutes longer (15 minutes total). Transfer to wire rack; cool 30 minutes.