In a large bowl (if using a stand mixer, go ahead and start it in that bowl) mix 1/2 teaspoon yeast, 2 cups high-gluten flour, and 1 1/4 cups water until it forms a thick batter. Cover with plastic wrap and let sit until bubbly, nearly doubled in size, and on the verge of collapse, about 2 hours.
Add 1/4 teaspoon instant yeast to the sponge and stir. Add the salt, malt syrup or powder, and and 1 1/2 cups flour. If using a stand mixer, stir a few strokes by hand to incorporate some of the dry flour with the sponge (this will help to prevent flour from flying everywhere when you turn on the mixer). Mix on low speed for about 2 minutes, or by hand for a few minutes or until a dough ball has formed. Slowly add the remaining flour, and mix on medium speed for 6 minutes (or knead by hand for about 10 minutes) or until all of the flour is incorporated. The dough should be smooth, stiff, stretchy, and not sticky or tacky. If the dough feels dry and tears easily when stretched, add a little water, a teaspoon at a time, and knead some more. If the dough feels sticky, add some flour.
Line a sheet pan with parchment paper and spray lightly with oil. Divide dough into 2 3/4 to 3 ounce pieces, or, if you don’t have a scale, into 9 equal pieces. (Reinhart recommends 4 1/2 ounce bagels, which I found to be too large and difficult to work with.) Roll each piece into a ball, place on parchment, cover with a damp towel and let rest for 20 minutes. With your finger or thumb, poke a hole in each piece and stretch to about an inch in diameter. Try to stretch the dough evenly to avoid thick and thin spots. Place on parchment, cover with a damp towel, and let rest for 20 minutes.
To test whether the bagels are ready to go into the refrigerator, fill a medium bowl with cool water. Drop one of the bagels into the water. It should float within 30 seconds. If it doesn’t, pat the bagel dry, return to parchment and let rest for another 10 minutes before testing again. If it does float, pat the bagel dry, cover the baking sheet with plastic wrap. Be careful to create an airtight seal, otherwise the bagels could dry out. Place in the refrigerator overnight (or for up to two days).
On the day you want the bagels (one or two days later):.
Preheat the oven to 500°F Line a baking sheet with parchment paper and mist with oil and dust with cornmeal. Bring a large pot of water to a boil, and add the baking soda. Have a slotted spoon ready. If you are topping with seeds or salt, have those out and ready.
Remove the bagels from the refrigerator. Place a few bagels into the boiling water. Be careful not to overcrowd the pot–the bagels will puff up a bit in the water. (I fit about 3 at a time.) Boil for 1 minute, then turn the bagels over and boil for another minute. Place on prepared parchment. (The bagels have a flatter side and a rounder side. Place the flat side down for a more rounded top.)
Bake. Place baking sheet on the middle rack on the oven and bake for 5 minutes. Reduce heat to 450°F, rotate the baking sheet 180° and bake for an additional 5-8 minutes, or until tops are golden brown. Remove from the oven and cool on racks for about 15 minutes. I.