Easy Sourdough Bagels

Mix starter, water, oil, flour, and salt together and then let rest for 10 minutes.Knead the dough with a dough hook on low speed for about 4 minutes - the dough will be very stiff.Transfer to a greased large bowl and let rise for 4 hours. Fold the dough over on itself 2 times (or try to- sometimes I don't always remember both folds)Pour out the dough onto a floured surface (a lightly floured tea-towel works great), knead a couple of times, flatten and cut into 12-18 equal pieces (about 5 oz. each).Shape the bagels by making each piece into a ball and using your thumb to punch a hole through the middle of the ball, stretching to make the center hole. Set the shaped bagels on a parchment or silicone lined baking sheet (12 will fit on one large sheet, if making 18, use two smaller sheets) - they are known for sticking, so this will make removing them much easier.Cover the shaped bagels with a damp towel (the one used for cutting works great) and let sit for about an hour.Fill a large 12-inch skillet ½ to ¾ full with water and add the tablespoon of soda. Bring it to a boil. Start the oven preheating to 450 degrees at this time.When the water is boiling, drop as many bagels as will fit, one at a time, into the boiling water. Boil for 1 minute, turning at the halfway mark. Use a slotted spoon to place the bagels back on the baking sheet. Continue until all the bagels have been boiled.Brush the bagels with milk or an egg glaze at this point, if you wish, and top with your desired toppings.Bake for 14 to 15 minutes, alternating pans at the halfway point if needed. Cool on a rack.