To make the dough: In a medium-sized bowl, combine the flour, pepper and salt and whisk to combine.

Add the cold cubed butter. Using clean fingers, smoosh the cubes of butter into the flour, coating each one with flour. You could also use a pastry cutter instead of fingers. Add the ice water and stir gently to combine, until the dough just starts to come together, but you should still see pea-sized pieces of butter. Dump half the dough onto a large piece of plastic wrap, and use the plastic to push the dough together into a ball.

Wrap tightly and refrigerate for 30 minutes. Repeat with the second ball of dough.

To make the filling: Pour the olive into a small frying pan over medium heat. Add the sliced leaks and a pinch of kosher salt. Cook until golden brown and caramelized, about 10-12 minutes. Set aside to cool for about 10 minutes.

Combine the feta, cottage cheese and black pepper in a small bowl; mix well. Add the cooled leeks and stir to combine.

To assemble: Preheat oven to 400 F.

Remove one disk of dough from the fridge and roll out on a well-floured board to an 1/8-inch thickness. Cut out circles using a 3-inch cutter. Brush each circle with egg wash. Spoon 1 1/2 teaspoons of the leek and feta mixture into the center of each circle.

Fold into a triangle, pinching the corners VERY well. Brush the tops and edges lightly with egg wash.

Place the hamantaschen back into the fridge for 10 minutes, then straight into the hot oven for 25-30 minutes, until golden brown.