"Custard mixture" refers to a blend of ingredients used to make custard, a creamy dessert. It usually includes eggs, milk or cream, sugar, and flavorings like vanilla. Full definition
When the custard and berry mixture is completely cool, stir them together and pour the blueberry custard mixture into the frozen bowl part of the ice cream machine. (strawberriesforsupper.com)
Fill each shell about 3/4 full with custard mixture. (health.com)
First, be sure that you cook the egg custard mixture long enough. (thespruce.com)