01 - In a large mixing bowl, combine bread flour, instant dry yeast, fine sea salt, and granulated sugar. Mix thoroughly to distribute all ingredients evenly.
02 - Pour warm water and olive oil into the dry mixture. Stir with a wooden spoon until a shaggy, rough dough begins to form.
03 - Knead by hand on a lightly floured surface or use a stand mixer with dough hook attachment for 5 to 7 minutes, until the dough becomes smooth, elastic, and passes the windowpane test.
04 - Gently fold the chopped spinach and drained cottage cheese into the dough. Continue kneading just until evenly distributed—the dough will feel slightly sticky from the cheese moisture.
05 - Transfer the dough to a lightly oiled bowl, turning once to coat all surfaces. Cover with plastic wrap or a clean kitchen towel. Place in a warm, draft-free area for 1 hour, or until the dough has doubled in volume.
06 - Position oven rack to center position. Preheat oven to 425°F. Line a large baking sheet with parchment paper.
07 - Turn the risen dough onto a lightly floured surface. Using a bench scraper or knife, divide the dough into 8 equal portions, approximately 4 ounces each.
08 - Form each portion into a smooth ball by tucking edges underneath. Flatten each ball to about 1/2 inch thickness. Press your thumb through the center to create a hole, then gently stretch and widen to form a 4-inch flattened ring.
09 - Place shaped flagels on the prepared baking sheet, leaving 2 inches between each. Cover with a clean towel and let rest at room temperature for 15 minutes to puff slightly.
10 - Brush the tops and sides of each flagel generously with beaten egg using a pastry brush. Sprinkle sesame or poppy seeds over the top if desired, pressing gently to adhere.
11 - Bake at 425°F for 18 to 20 minutes, rotating the baking sheet halfway through for even browning. The flagels are done when they develop a deep golden brown crust and sound hollow when tapped on the bottom.
12 - Transfer flagels to a wire cooling rack. Let cool completely for at least 30 minutes before slicing or serving to allow the crumb structure to set properly.