1. Combine 2 cups of the half-and-half, the sugar, and the salt in a medium saucepan and stir. Put over medium-low heat. Cook until the mixture just begins to steam, 2 or 3 minutes.
2. Combine the cornstarch and the remaining 1/2 cup half-and-half in a bowl and whisk to make a slurry; there should be no lumps. Add the slurry to the mixture in the pan and raise the heat a little if it’s not steaming yet. Cook, stirring occasionally, until the pudding thickens and just starts to boil, 3 to 5 minutes. Reduce the heat to the low setting that holds a gentle but steady bubble and continue to cook, stirring constantly, until it thickens noticeably and starts to stick to the pan, another 3 to 5 minutes. Stir in the butter and the vanilla extract.
3. Pour the pudding into a bowl big enough to hold it or into 4 to 6 small ramekins or glasses. Put plastic wrap directly on top of the pudding to prevent the formation of a “skin.” (Or if you like pudding skin, leave the bowl uncovered.) Refrigerate until chilled, at least an hour, and serve within a day.

— Recipe from How to Cook Everything: The Basics