The essential ingredients for the Orange Balls recipe include soft butter, egg yolk, orange zest, fresh orange juice, sugar, sunflower oil, baking powder, and all-purpose flour. The soft butter and egg yolk provide moisture and richness to the dough, ensuring the cookies are tender and melt-in-your-mouth delicious. The addition of orange zest and juice is crucial, as they infuse the cookies with a vibrant citrus flavor that balances beautifully with the sweetness from the sugar. Sunflower oil helps create a light texture, while baking powder ensures the cookies rise properly, resulting in a charmingly airy feel. Finally, the all-purpose flour acts as the structural component that holds everything together, leading to the perfect consistency for rolling into balls.