In a large bowl, combine 1 1/4 cups AP flour, 1/4 tsp yeast, and 3/4 cup lukewarm water. Mix until cohesive, then cover and rest for 4-6 hours.
When poolish is bubbly and ready, add 1 1/2 cups lukewarm water and mix. Then, add 4 3/4 cups AP flour, 3/4 tsp yeast, and 2 1/2 tsp salt.
Mix dough with a chopstick or fork until shaggy. Then, transfer to a clean work surface and knead for 5 minutes until a cohesive dough forms.
Place your dough in a clean, lightly-greased bowl for 2 hours, covered, folding the dough on top of itself on all 4 corners 2-3 times after the first hour. Then, refrigerate for 8-12 hours.
Remove dough from fridge and let come to room temperature for 1 hour.
Weigh and divide dough into 12 equal pieces. Form each piece of dough into a tight ball and place on a baking sheet or counter, covered, and rest for 30 minutes.
Next, form a hole in the middle of each ball with your finger and stretch the bagel hole to 2-3”. It will shrink when it rises.
Let the bagels rest another 30 minutes, covered. In the meantime, heat a large sauté pan, dutch oven, or pasta pot with about 4 quarts of water and bring to a boil. Add molasses and 1 tbsp salt when bubbling and stir.
Fill a baking sheet with black sesame seeds. Then, 3 at a time, transfer your proofed bagels into the boiling water mixture and cook for 45 seconds on each side.
Remove bagels with a slotted spatula and place directly onto the black sesame seeds. Shake pan and press gently to adhere. Then, transfer each bagel, sesame seed side up, onto a parchment-lined baking sheet (6 on each).
Preheat oven to 475°F. Boil the rest of your bagels in batches of three and cover with sesame seeds.
Bake both sheets of 6 bagels in the same preheated oven for 18-23 minutes, switching racks halfway.
Let cool for 10-15 minutes before slicing and serving.