Add your potatoes and a good pinch of salt to a saucepan of boiling water and boil until soft.
Meanwhile, heat your olive oil in a frying pan on a moderate heat and add your spinach.
Once it has wilted, add a splash of water (around 2 tablespoons) and your tomato paste and mix into your spinach.
Now add your spices and seasoning and stir in.
Allow your spinach to simmer until most of the liquid has evaporated.
Remove from the heat.
Smash your potatoes with a fork and mix into the spinach.
Leave this to one side and allow to cool.
Now take one sheet of yufka and fold it in half, carefully, to make a semicircle.
Using a sharp knife, start from half way along the flat edge and cut downwards to the curved edge, to halve the semi circle.
Now take one of those pieces and open it out.
Again, cut down the centre from the flat edge to the curved edge so that you have two triangles.
Place one of the yufka triangles onto a clean, flat work surface with the curved edge at the bottom and the point at the top.
Carefully place the rest of the yufka under a damp cloth so that it doesn't dry out.
Now, using a pastry brush, paint your yoghurt egg wash emulsion all over the yufka triangle.
Take 3 teaspoons of the potato and spinach mix and carefully arrange it along the bottom edge of the triangle, leaving a couple of centimetres space at each edge.
Now take the bottom edge and loosely roll the yufka until you reach the pointed edge, creating a long sausage shape.
Now take one end of the sausage shape and carefully start to create a spiral shape.
When you reach the opposite end, tuck the loose edge of yufka under the base of your spiral (your rose) and carefully lay it on a baking tray.
Repeat this process until you have used all of your yufka or potato and spinach mix.
Preheat your oven to 220 degrees Celsius.
Now paint the rest of your yoghurt egg wash over the top of your gül böreği rose shapes and sprinkle each one with nigella seeds.
Place your güle böreği in the centre of the oven and bake for 20 minutes or until golden brown on top.
Once the pastries are golden brown, remove from the oven and leave to cool to room temperature.
Enjoy your potato and spinach rose börek as a snack or as part of a main meal.