Preheat oven to 375F and line a baking sheet with parchment paper.
In a bowl, whisk together the flour, baking powder, and salt. Add the yogurt and mix together with a fork or spatula. The dough will be crumbly.
Dust your work surface with flour, then place the dough on top. Knead the dough until it is tacky, but not quite sticky. If you are adding blueberries to your bagel, add about ¼ to ½ cup at this step and lightly knead in. It should not leave dough on your hands when you pull away – feel free to add more flour as you knead if necessary.
Divide the dough into 4 equal balls. Use your thumb to poke through the center of each ball and gently stretch and work the dough to form a bagel shape. Place formed dough on the lined baking sheet.
Brush your bagels with your whisked egg, and top with desired toppings.
Bake on the top rack of the oven for 25 minutes. Allow to cool before cutting.