In the bowl of a stand mixer, combine the starter, milk, flour, and brown sugar with the batter beater on low speed. You just need it to be combined.
Switch to the dough hook and mix on medium-low speed until the dough is smooth, strong, and rubbery. It is a stiff, strong dough. This should take 2 or 3 minutes.
Dump the dough on the counter (you don't need to add any flour to the counter) and knead by hand for a few turns, or until the dough turns into a satiny, tight ball. Check the gluten development by stretching a small piece of the dough between two fingers. It should stretch really thin without breaking (this is called the windowpane test).
Cover the dough with plastic wrap and allow it to rest on your counter for 10 minutes.
Divide the dough ball into 12 equal pieces and roll them into balls.
Cover with plastic wrap and allow them to sit at room temperature for another 10 minutes.
Line a cookie sheet with parchment paper and liberally sprinkle it with flour.
Roll each ball into a snake about 8-10" long.
Wrap the snake around your hand, overlapping the ends in your palm about 2".
Turn your hand over and roll the dough on the counter, fusing the ends together. If the dough seems dry and doesn't want to fuse, give it a spritz of just a tiny bit of water to help it.
Place the bagels on the cookie sheet, cover with plastic wrap and allow to proof for 1-3 hours at room temperature. They are done when they look and feel puffy. This could take more time if your house is cold, or less time if your house is warm. They will not double in size. You can test that they are done by placing one in a bowl of cold water. If it floats, it is done. Remove the bagel from the cold water and dry it off before replacing it on the cookie sheet.
Place the covered cookie sheet in the fridge to proof for at least 4 hours, or up to 12 hours.
Prepare a wire rack with a towel under neath it. Remove the bagels from the fridge and place the cookie sheet next to the wire rack.
Place a bowl next to the racks and fill it with the everything bagel mixture.
Preheat the oven to 425F.
When the oven has been fully preheated, place a large pot of water on the stove top to boil. You want to give the oven a good long head start at heating so it is nice and hot, so don't rush it.
Carefully take the bagels off of the cookie sheet and wipe off any excess flour from them and place the bagels on the wire rack. Leave the cookie sheet with any remaining flour where it is, you still need it.
Add the baking soda to the boiling water.
Carefully drop the bagels, one or two at a time, into the boiling water.
Allow them to cook for 30-40 seconds per side. They should float.
Carefully remove the bagels and place them on the wire rack for 30 seconds to drain off any excess water.
Then place the bagels, upside down, into the bowl of everything bagel mixture.
Place the bagels, right side up, back on the cookie sheet. Repeat with remaining bagels.
Place the cookie sheet with the bagels into the oven. Immediately turn the temperature down to 400F.
Bake for 12 minutes, and then open the oven door briefly to release any steam in the oven. Bake an additional 12-14 minutes, or until the bagels are golden brown.
Remove to a wire rack to cool completely.
Enjoy!
Notes
This recipe works best with a high gluten flour like bread flour, but unbleached all purpose will work, too!Note: If you want a chewier bagel, boil them for up to 1 minute per side. If you want a softer bagel, boil them fro only 20 seconds per side.