Add starter, water, sugar, and salt to the bowl of a stand mixer. Mix until combined.
Add flour one cup at a time allowing it to incorporate before adding another cup.
Cover with plastic wrap or a damp tea towel. Allow to sit overnight at least 8-12 hours.
Cut dough in 8 equal balls.
Put a hole in the center of each ball slightly stretching the hole until it looks like a bagel.
Allow the bagels to rest on a parchment paper lined baking sheet until puffy. This may take a few hours depending on the temperature of your kitchen.
Preheat oven to 425°F.
Put a large pot of water on the stove and bring to a boil. Add the baking soda and brown sugar to the boiling water.
Boil bagels for 60 seconds on each side then place back onto the parchment paper lined baking sheet. If using any toppings, put them on the bagels directly after boiling.
Bake bagels at 425°F for 20-25 minutes.