Preheat oven to 375*.
Prep two cookie sheets. Either butter them well, or line with unbleached parchment paper. (*See recipe notes below.) Mix flour, baking powder, and salt. Add yogurt or sour cream and mix/knead until combined. Add any optional ingredients and mix. The dough will be unlike other bread dough you've worked with, it's sort of sticky and clumpy.
Get more flour on your hands or soft butter so the dough doesn't stick (it still will a little, but it's okay) then pull out a handful of dough a little smaller than baseball size and roll into a ball. Flatten just a bit and poke a hole in the middle with your fingers before setting onto the cookie sheet. Feel free to make yours a little fatter, but you'll obviously get less bagels out of each batch than I did. If it starts sticking to your hands, just get more butter or flour on them.
Brush each bagel with the beaten egg mixture then sprinkle on your toppings of choice. I did one cookie sheet with a light sprinkling of sea salt only and the other cookie sheet with a little garlic powder, a little sea salt, then a few sesame seeds. If desired, flip the bagels and do the other side too.
Bake 25-28 minutes on the top oven rack or until lightly golden. If your oven runs hot, just make sure they don't burn on the bottom. As you can see in the photo, some of them got more golden brown than others, so you may want to rotate the pans partway through baking. Let cool before slicing or you'll just smoosh them.
Serve with lots of real butter, of course, and/or some organic cream cheese.
Store in the fridge so they'll keep longer, since there are no preservatives in them, obviously. If you have extra (doubtful), slice in half and put them in a freezer bag, but don't put the two halves together like a sandwich. Instead stagger the tops and bottoms so they're easier to pull apart later and pop into the toaster for a fast morning breakfast.