Preheat the oven to 350 degrees Fahrenheit.
In a large bowl, add the thawed spinach, crumbled feta cheese, fresh herbs, 1 egg and season with salt and pepper. Stir to combine well.
In the 2nd bowl, add the glaze ingredients. Whisk the melted butter, milk, olive oil and egg until well combined. And in the 3rd bowl, add the topping glaze ingredients and whisk the milk and egg.
Unroll phyllo sheets and cover with a damp towel to keep it from drying. If your box of phyllo has 2 rolls of phyllo, just use 1.
Brush a 9 by 13 pan with the butter glaze mixture on all sides and bottom.
Layer the first phyllo sheet into the pan and brush with glaze. Continue this for 10 layers or about half of the phyllo sheets.
Add the spinach and feta filling and distribute evenly. Then top with another sheet of phyllo and continue layering a phyllo sheet, then brushing with glaze until all the sheets are used up.
Once all the phyllo sheets are used, brush with the topping glaze and use a sharp knife to cut the borek into 12 squares or 24 triangles.
Bake the spinach borek at 350 degrees Fahrenheit for 40-45 minutes or until the top is golden brown.