In a medium sauce pan add the sugar, cornstarch, and salt. Whisk to combine.
While whisking, slowly add the half-and-half until till combined.
Add the egg yolks and whisk to combine.
Over medium-high heat bring the mixture to a simmer, whisking constantly but gently. Reduce the heat to medium and cook, stirring constantly, until the pudding thickens and coats the back of a spoon, about 2 minutes.
Remove from the heat and add the butter and vanilla, stir to combine. Pour the hot pudding into six 1-cup wide-mouth mason jars, filling the jars an inch from the top. Add a flat lid and then screw on the ring to close the jars.
Refrigerate until the pudding is set, about 3 hours.
Eat the pudding right out of the mason jars. Add sprinkles before eating for extra smiles.
Notes
You can swap the half and half for 3 cups of whole milk.
You don't have to add this to individual jars, it's just fun. You can place the pudding in a large bowl to serve instead of 6 individual containers.
You can use salted butter, just omit the salt in the recipe.