Fill a large bowl with cold water and ice. Set aside.
Whisk the yolks and 1/4 cup of the sugar until light and creamy, about 2 minutes. Set aside. Heat the cream, milk, remaining 1/2 cup of sugar, and salt in a medium pot and cook on medium heat for 2-3 minutes, until the sugar is dissolved and the milk is nearly simmering. Lower the heat and scoop a 1/2 cup of the milk mixture into the creamed yolks, whisking the entire time to combine. Scoop another 1/2 cup of milk into the yolks, whisking the entire time to combine. Pour the heated yolk mixture back into the pot, again whisking the entire time to combine. Then, using a spatula, slowly stir the custard mixture while it heats. The custard should thicken in 3-5 minutes. You will know it’s ready when it coats the back of a spoon and holds its shape when you draw your finger through it. Quickly remove from heat and stir in orange zest, lemon juice, and vanilla extract. Immediately pour into a bowl, and place bowl in the ice bath to cool the mixture.
Once ice cream chills to a warm (not hot) temperature, cover with plastic wrap and allow to chill in the freezer for at least 3 hours, and up to overnight.*
Once chilled, make chocolate chips. Melt the chocolate in a microwave-safe bowl in 30 second increments, stirring in between each heating. Pour onto a parchment-lined cookie tray and spread thinly with a spatula. Sprinkle with salt and place in freezer for 10-15 minutes. Finely chop the chocolate and set aside.
Pour ice cream into your ice cream maker and churn according to manufacturer’s instructions. 2 minutes before removing from ice cream maker, stir in chocolate chips. Transfer to freezer-proof container and allow to harden for at least 12 hours. Then serve!
*If chilling overnight, chill in fridge and not freezer