Add room temperature margarine, oil and baking powder and mix. Slowly add flour to this mixture and knead until it reaches the consistency of an earlobe. Divide the dough into 3 parts and keep it in the refrigerator for 1-2 hours.
Take the dough out of the fridge and use a rolling pin to roll it into a round shape about 1 mm thick and spread 2 tablespoons of tahini on it evenly. Sprinkle sugar and walnuts on top. Carefully roll the dough into a roll.
Brush the rolled dough with egg yolk, sprinkle sesame seeds and cut into two-finger-thick slices. Place the slices on a baking tray lined with baking paper. Bake in a preheated oven at 180 degrees for about 20-25 minutes. Serve warm.
