Add olive oil and gently saute the onions and garlic until translucent.
Stir in the tomato paste, chili, salt, pepper, and paprika, and saute for another minute.
Add the spinach and cook for a few minutes on high heat until the water from the spinach totally evaporates.
Remove from the heat and let it cool down before using for borek.
Preparing the Sauce
Put 2 egg whites+ and 1 whole egg in a bowl and whisk lightly.
Pour in the milk and vegetable oil and whisk to combine. Set aside to use when required.
Shaping the Rose Shaped Borek
Preheat the oven to 180° C - 360° F (fan oven).
Line a rectangular baking tray size of 35cm x 25 cm or a round tray size of 28cm dia with a baking sheet.
Lay a piece of yufka on a work surface and scatter 2-3 tablespoon of the sauce on it, spread the sauce evenly using a pastry brush.
Divide the filling into 3 and scatter ⅓ of it on yufka evenly. Then cut the yufka in quarters. You will have 4 large triangles.
Take one of the triangles and roll it starting from the large side into a long sausage shape.
Swirl the long sausage into a rose shape, and tuck the loose end piece underneath the rose.
Repeat the same for the rest of the yufka pieces, you should have 12 roses out of 3 yufka sheets.
Place them on a baking tray and brush with melted butter and then egg yolk.
Sprinkle on sesame seeds or nigella seeds.
Place the tray in the oven and cook the boreks for 40 minutes or until golden brown.
Notes
Make sure the oven is heated to 180° C - 360° F (fan oven) before you put the borek in. A cold oven would cause a longer cooking time and less crispy pastries.
You can make the spinach filling a day before and keep it refrigerated until you need it.
Wash your spinach leaves thoroughly and dry them using a salad spinner or leave them on a colander until the leaves are dry.
Turn your fresh garlic into a paste with a or grate it using a .