In a medium bowl, combine the salt, sugar, yeast, milk, yogurt, water, egg, butter and cheese. In the bowl of a stand mixer fitted with a paddle attachment, mix on medium speed to combined very well.

Gradually add the flour mixed with baking powder, mixing on low till combined to give a sticky dough.  Knead until smooth and sticky about 5-7 minutes. Grease large bowl with some oil and grease your hands too so you can handle the dough, Place the dough in the greased bowl, cover with plastic wrap and allow it to rise for half an hour.

Divide the dough into 6-7 balls, roll out each balls into a circle and cut the circle into triangles. Place a teaspoon of cheese closer to the large end of the triangle, beginning at the widest point of the triangle where the filling start rolling it (Gently without pressure) towards the narrowest point. Place the croissants on a lightly greased baking sheet. Continue to do this with the rest of the dough.

In a small mixing bowl, whisk the egg yolk with milk and vanilla, brush each croissant. Top each croissant with sesame seeds mixed with nigella.

Bake for 15 minutes, or until golden light. Let cool completely on a wire rack and serve!