01 - Combine bread flour, instant yeast, sea salt, and granulated sugar in a large mixing bowl. Mix thoroughly to distribute all ingredients evenly.
02 - Pour warm water and olive oil into the flour mixture. Stir with a wooden spoon until a shaggy, rough dough forms and all dry ingredients are incorporated.
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 pulls away from the sides of the bowl.
04 - Gently fold chopped spinach and drained cottage cheese into the dough. Continue kneading briefly until evenly distributed—the dough will feel slightly tacky due to the cheese.
05 - Transfer dough to a lightly oiled bowl, turning once to coat. Cover with plastic wrap or a damp towel and place in a warm, draft-free area for 1 hour until doubled in volume.
06 - Preheat oven to 425°F. Line a large baking sheet with parchment paper and set aside.
07 - Turn risen dough onto a lightly floured surface. Divide into 8 equal portions using a bench scraper or sharp knife.
08 - Form each portion into a smooth ball. Flatten balls to 1/2 inch thickness. Press your thumb through the center and gently stretch to create a 4-inch flattened ring with a visible hole.
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 puffed.
10 - Brush the tops of each flagel with beaten egg using a pastry brush. Sprinkle evenly with sesame seeds or poppy seeds if desired.
11 - Bake for 18 to 20 minutes until deep golden brown and the internal temperature reaches 190°F. The flagels should sound hollow when tapped on the bottom.
12 - Transfer flagels to a wire cooling rack. Allow to cool for at least 30 minutes before slicing or serving to complete the cooking process.