In a mixing bowl, combine the flour, water, sourdough starter, salt, and sugar. Mix thoroughly until the dough becomes smooth and slightly sticky, using either your hands or a stand mixer.
½ cup sourdough starter, 1 cup warm water, 2 tablespoons sugar, 2 teaspoons salt, 4 cups bread flour
Transfer the dough to a lightly floured surface and knead until it is smooth and elastic, which helps develop gluten for a chewy texture. Let it rest for a few hours until it has doubled in size.
Divide the dough into portions about the size of a tennis ball. Roll each portion into a ball, then poke a hole in the center and gently stretch it to create an opening about 1.5 to 2 inches wide. Repeat with the remaining dough to form a total of 8 bagels. Place them on a parchment-lined baking sheet and allow them to rise again for about 2 hours, until they double in size.
Bring a large pot of water to a boil. Carefully lower the bagels into the water, cooking them for 1 minute on each side. Transfer them back to the baking sheet.
While the bagels are still wet, press your desired toppings onto the surface so they adhere easily.
Everything But the Bagel seasoning
Preheat the oven to 400ºF (200ºC). Arrange the bagels on a parchment-lined baking tray and bake for 25 minutes, or until they turn golden brown.
Serve and enjoy!