Once it's slightly cooled, add the egg and stir until absorbed.
In a casserole with 4/5 cup (200 ml) warm water, add the oil and salt it lightly.
In an oiled tray, place 4 phyllo pastry sheets in a cross in such a way so that 1/2 of each spills out of it.
Next, smear the sheets on the bottom of the tray with a brush dipped in the oily water.
Place a sheet on top, fold it in a bit so it fits at the bottom of the tray, smear with the water and arrange the next sheet.
Do this for 4 sheets. On the 4th, smeared with water, pour on 1/2 the mince and leek mixture.
Then place another 4 sheets smeared with water as well and pour on the rest of the mince mixture. Finish the burek off with the remaining 4 sheets.
Finish forming the burek by folding in the 1st 4 sheets toward the middle and smooth out with the brush after dipping it in the watery mixture.
Leave thus prepared burek for 5 min., then place in the oven and turn it up to 356°F (180 °C).
After about 30 min., the burek will be ready.
Cover it with a towel for 10 min. and then serve.