Creating the perfect custard for your Orange Pastry requires careful attention to the cooking process. Start by heating the milk just until it’s warm, not boiling, as this can lead to curdling. When mixing the cornstarch with the egg yolks and sugar, ensure that it’s well combined to create a smooth base that will help the custard thicken. As you pour the warm milk into the yolk mixture, do so slowly while whisking continuously to temper the eggs and prevent them from cooking too quickly. Once you return this mixture to the saucepan, keep stirring over medium heat until you notice a significant thickening. Patience is key! Once thickened, make sure to incorporate the butter, which not only adds richness but also contributes to a silky texture. If you follow these steps carefully, your custard should be perfectly thick and smooth, complementing the pastry beautifully.