01 - Combine bread flour, instant yeast, sea salt, and granulated sugar in a large mixing bowl. Mix thoroughly to distribute yeast and salt evenly throughout the flour.
02 - Pour warm water and olive oil into the flour mixture. Stir with a wooden spoon until a shaggy, rough dough forms and no dry flour remains visible.
03 - Knead by hand on a lightly floured surface or use a stand mixer with dough hook attachment for 5-7 minutes until dough becomes smooth, elastic, and passes the windowpane test.
04 - Gently fold chopped spinach and drained cottage cheese into the dough. Knead briefly until evenly distributed—the dough will feel slightly sticky due to the cheese moisture.
05 - Transfer dough to a lightly oiled bowl, turning once to coat all surfaces. Cover with plastic wrap or a damp towel and place in a warm, draft-free area for 1 hour until doubled in volume.
06 - Set oven to 425°F. Line a baking sheet with parchment paper and set aside.
07 - Punch down risen dough and turn onto a lightly floured surface. Divide into 8 equal portions using a bench scraper or knife.
08 - Roll each portion into a smooth ball, then flatten to approximately 1/2 inch thickness. Press your thumb through the center and gently stretch to form a 4-inch flattened ring with a hole in the middle.
09 - Arrange shaped flagels on the prepared baking sheet, leaving 2 inches between each. Cover with a clean towel and let rest for 15 minutes until slightly puffy.
10 - Brush the tops of each flagel generously with beaten egg using a pastry brush. Sprinkle with sesame seeds or poppy seeds if desired, pressing lightly to adhere.
11 - Bake for 18-20 minutes until flagels 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 prevent steam from making the interior gummy.