• 4 cups whole milk
• 1 tablespoon vanilla extract
• 1 teaspoon butter
• 4 eggs
• ½ cup white sugar
• 3 tablespoons cornstarch

Place milk, vanilla extract, and butter in a saucepan. Cook and stir over medium heat until simmering; remove from heat before it comes to a boil. Whisk eggs, sugar, and cornstarch together in a bowl until sugar dissolves. Set the saucepan back over low heat. Pour in egg mixture slowly, whisking constantly, until custard thickens enough to coat the bottom of a spoon, 5 to 10 minutes. Serve warm or transfer custard into a large bowl, cover, and allow to cool before chilling.