Nancy Silverton's recipe for sourdough bagels comes from her classic book, Breads From The La Brea Bakery. Food Guy and "Baking Wizard" Greg Patent doesn't rely on Silverton's beloved recipe to satisfy just his summertime bagel-baking jones. He even uses a sourdough starter begun years ago following Silverton's in-depth instructions.
Besides sourdough starter, you'll need a few special ingredients to make proper bagels, particularly some high-gluten flour. Greg recommends a 14% protein content. If you can't find this locally, plan ahead and order some specially. Without that high gluten percentage, the bagels won't be chewy. And a bagel that is not dense and chewy is merely a bagel wanna-be.
Other ingredients you'll need include malt syrup (for flavor, and to break down the starches in the flour), sugar, water and yeast. Silverton calls for cake yeast, which may be hard to find; substitute instant yeast.
After you've form the dough, you'll knead it. Be prepared for a very stiff dough. After kneading, give the dough a short rest, then divide it into 4 oz portions, rolling each one into an 8" long cylinder. Wrap each one around your hand, and roll the 1 1/2 inches of overlapping dough on the countertop to form a seam. To keep that bagel hole open, cut up a cardboard paper towel ring into three-inch sections and insert one section into each bagel-dough ring.
Put the bagels on several parchment paper-lined trays, cover them with towels, and leave them overnight in the refrigerator
The next day, boil four inches of water, and remove the pieces of cardboard. Drop a few bagels into the water and boil them for twenty seconds. This step is important: it cooks the starches on the dough's surface. Remove them from the water, put them on the parchment-lined pan, and bake them at 400 degrees F. until they're golden-brown. If they look burned on the bottom, don't worry; they aren't.
You heard it from the Food Guys: bake your own bagels.