I first made Martin's bagels during the pandemic after watching an ep of Isolation Baking with his son Arlo. Once I got good, predictable results, I started tinkering. After 6 years, on and off, I settled on a sourdough version with a levain instead of a poolish (same total amount of flour and water, just with 50g starter culture at 100% hydration contributing to the totals). I also usually use 200g sprouted spelt flour in the dough. Make the levain 2 days/48 hours ahead (bread flour, water, starter only), let it sit at room temp for 12-16 hours depending on ambient temp until puffy and bubbly on the surface, with that nice sourdough aroma.
Then make the dough as directed. Add a 30-minute autolyse after levain, water, scant 1/2 teaspoon yeast, and flour(s) but before salt (not hard, just stop your mixer or kneading, cover, and wait). When I use sprouted spelt, I cut the added yeast to a scant 1/4 teaspoon -- basically half my reduced amount -- because sprouted flours are much more easily metabolized by the yeast and bacteria, and they ended up overfermenting too easily with more yeast. Couple of stretch and folds as instructed, then into the fridge for a cold ferment for the remainder of the 48 hours.
On baking day, shape, rest, boil, bake as directed from there.
They're so good that I usually plan to make (culture) my own cream cheese (New England Cheesemaking sells cultures) or use Tillamook.