Cream butter and sugar in a large bowl of a stand mixer until pale and thick (make sure to use the paddle attachment). This should take approximately 3-5 minutes. Make sure to scrape down the sides of the bowl.
Add your eggs one by one ensuring they are mixed well.
In a separate jug combine the orange juice, zest, vanilla, baking powder and soda. Stir and add this back to creamed butter mixture. Mix again until well incorporated.
At low speed, slowly add the flour (I like to use a large spoon to do this), making sure it is mixed well before adding the next one. Repeat until all the flour is used and you have a soft dough.
Check the dough with your fingers - it should feel soft (not sticky) - yet pliable. Cover with plastic wrap and allow the dough to rest for half an hour in the fridge. (see note 1)
Using an ice cream scoop, scoop out the dough and form it into a ball. If you want to be super precise, you can weigh your koulourakia - for reference, mine weighed 30 grams - approx. 1.5 oz
Using your hands, roll out the dough into a long rope - approx. 20 cm (7-8”) and form into your desired shapes. You can do plaits, “snails”, S shapes and pinwheels (refer to picture below).
Preheat your oven to 170 deg C - 340 F (NOT fan-forced) and place the cookies on a baking sheet lined with parchment paper. Brush with egg wash and sprinkle over sesame seeds.
Cook for 20- 22 mins until they have coloured. Leave them on the baking sheet for 5 mins. Then gently transfer to a wire rack to cool completely. (see note 2)