Combine sourdough starter, water, all-purpose flour, wheat gluten, dried onions, malt extract and salt to the bowl of a stand mixer, and mix and knead for ~5 minutes. Add to an oiled bowl, and place in a warm area or proofer. After one hour, fold the dough over on itself 3 times. Repeat the process 2 more times. Roll out the bagels as shown in the recipe, and place on parchment paper with some cornmeal on it. Spray some food service film with oil and place it on top of the bagels. Refrigerate overnight. After refrigeration, remove bagels to a warm area and allow to rise until puffy. This took about 2 hours but that’s going to depend on how warm your area is. After the dough is puffy, bring 1 gallon of water to a boil with sugar and baking soda. Boil the bagels for 30 seconds on each side, and place on 2 cookie sheets with parchment. Brush with egg/water mixture and sprinkle on your toppings. Bake in a pre-heated 450 degree Fahrenheit oven for 17-20 minutes, rotating once somewhere in the middle of that time. Bagels should be golden brown.