Combine flour, 1 Tablespoon granulated sugar, yeast and salt in the bowl of a stand mixer fitted with a dough hook attachment*. Mix to combine.
Add the sourdough discard, raisins, and ground cinnamon. With the mixer on low speed, slowly add the warm water until combined. Increase speed to medium and knead for 4-5 minutes (or knead by hand) until a smooth dough forms. The dough should not be sticky. If needed, add more water or flour (1 Tablespoon at a time) to reach the right dough consistency.
Transfer the dough to a large, greased bowl and cover with plastic wrap. Let the dough rise for 1 ½-2 hours at room temperature, or until doubled in size.
Prepare 2 baking sheets lined with parchment paper or a silicone baking mat and set aside.
Turn the dough onto a work surface, and divide into 8-10 equal-sized pieces (you can eyeball this, or use a kitchen scale to measure exactly). 8 pieces will make 8 large bagels; 10 pieces will make 10 smaller bagels. Using one palm for friction, roll each piece of dough into a smooth ball with the seam-side against your palm. Press your thumb through the center of the ball to create the hole. Stretch the hole to reach your desired bagel shape (keep in mind these will rise and expand so make the hole larger than you think it should be). Place the bagels on the prepared baking sheets. Cover with plastic wrap or a clean kitchen towel and let rise for 30 minutes while you prepare the next step.
Preheat oven to 425°F. Bring a pot with 2 quarts of water and 2 Tablespoons of granulated sugar to boil.
Place the bagels in the boiling water for 15-30 seconds on each side**. The bagels should float (if not, see notes below). You can likely fit 2-3 bagels in the pot at a time, just make sure there is enough room for them to float openly as they will expand. Remove from the boiling water using a slotted spoon, shake off any excess water, and return to the baking sheets. If needed, you can reshape the bagels a little after they've cooled.
Bake for 20-22 minutes or until golden brown. Transfer to a cooling rack to cool before slicing and serving.
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Notes
*This recipe can be made without a stand mixer. To do so, mix the dough in a large bowl with a wooden spoon, then knead by hand. **Boiling for a longer time will give you a thicker bagel crust. To make this recipe with active sourdough starter, omit the yeast and replace the sourdough discard with active starter (200g). You will also need to increase the rise times. Passing the Float Test: The bagels should "pass the float test" to indicate that the dough has risen enough and the bagels will be light and fluffy. If your bagels do not float when you add them to the boiling water, cover the unboiled bagels with a clean kitchen towel and let rest for another 10 minutes. Then, try again.