To achieve the ideal golden and flaky texture of your Berry Pastries, several key factors should be taken into consideration. First, make sure your puff pastry is kept cold, as warm pastry can lose its flakiness during baking. Second, when you brush the egg yolk-milk mixture onto the edges, do so lightly—this will encourage even browning without weighing down the pastry. Additionally, baking the pastries in a preheated oven is crucial; this helps the puff pastry rise quickly and evenly, leading to that coveted golden crust. Finally, keep a close eye on your pastries as they bake; every oven is different, and slight adjustments in baking times may be necessary to achieve that perfect finish.