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 - Add warm water and olive oil to the dry mixture. Stir vigorously until a shaggy, rough dough begins to form and all flour is incorporated.
03 - Knead the dough by hand on a floured surface or use a stand mixer fitted with a dough hook for 5 to 7 minutes. Work until the dough becomes smooth, elastic, and pulls away from the sides of the bowl.
04 - Gently fold in the chopped spinach and drained cottage cheese. Continue kneading just until evenly distributed throughout the dough. The dough will remain slightly sticky due to 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 towel and place in a warm, draft-free area. Let rise for 1 hour or until doubled in volume.
06 - Preheat oven to 425°F. Line a large baking sheet with parchment paper and set aside.
07 - Turn the risen dough onto a lightly floured surface. Using a bench scraper or knife, divide 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 the opening to form a 4-inch flattened ring.
09 - Arrange the shaped flagels on the prepared baking sheet, leaving 2 inches of space between each. Cover loosely with a clean towel and let rest for 15 minutes to puff slightly.
10 - Brush the top surface of each flagel with the beaten egg using a pastry brush. Sprinkle sesame seeds or poppy seeds evenly over the tops, pressing gently to adhere.
11 - Bake for 18 to 20 minutes, rotating the baking sheet halfway through for even browning. The flagels are done when deeply golden brown and the bottoms sound hollow when tapped.
12 - Transfer the baked flagels to a wire cooling rack. Let cool for at least 30 minutes before slicing or serving to allow the crumb structure to set properly.