In a large bowl, combine the warm water, instant yeast, and barley malt syrup; stir to dissolve.
Add the bread flour and fine sea salt. Mix until a shaggy dough forms, then knead by hand or with a dough hook on low until very stiff, smooth, and elastic, 8β10 minutes.
Form the dough into a tight ball, return it to the bowl, cover, and let rise at room temperature until slightly risen and springy, 60β75 minutes.
Line two baking sheets with parchment. Divide the dough into 8 equal pieces. Shape each into a tight ball by cupping your hand and rolling on the work surface. Rest the balls, covered, for 10 minutes.
Shape the bagels: poke a hole through the center of each ball with your thumb, then gently stretch and rotate to a 2-inch hole (the dough will spring back).
Arrange the shaped bagels on the prepared sheets, cover, and refrigerate 12β24 hours for best flavor and chew, or let them proof at room temperature until slightly puffy, 20β30 minutes.
When ready to boil and bake, preheat the oven to 450Β°F. In a wide pot, bring the 4 quarts water, baking soda, and the barley malt syrup to a gentle boil.
Boil the bagels in batches: add a few at a time and simmer 30β45 seconds per side until slightly puffed and tacky. Remove with a slotted spoon and drain briefly.
While still tacky, top as desired: sprinkle sesame seeds, poppy seeds, everything bagel seasoning, or coarse kosher salt on the domed side.
Bake on the center racks until deep golden brown with a thin, crisp crust, 16β20 minutes. Cool on a rack at least 20 minutes before slicing.