To your stand mixer bowl with a dough hook, add sourdough discard, yeast, sugar and warm water.
Mix and let rest for 5 minutes until the yeast becomes foamy.
Add bread flour and salt.
Knead until combined.
Cover with an airtight lid or transfer to an airtight bowl and let it rest until it has doubled in size, about 90 to 120 minutes.
Once the dough has doubled in size, tip it onto a lightly floured surface. Divide the dough into 8 or 12 equal portions, depending on the size of bagels you would like.
Shape each portion into a ball, and then gently stretch the dough to widen the hole and form a bagel shape.
Arrange the bagels on a baking sheet, leaving space between them.
Let bagels rest for 30 minutes.
Preheat your oven to 400°F.
Bring a large pot of water to a boil. Reduce to a simmer and add baking soda.
Carefully add each bagel into the simmering water and boil for 1 minute on each side. Remove with a slotted spoon and add to the baking sheet.
Add toppings or brush the tops with an egg wash.
Bake for 20 to 25 minutes, or until golden brown.
Transfer bagels to a wire rack and cool completely.