In a medium saucepan, whisk together the granulated sugar, cornstarch, and salt.

Slowly pour in the milk, whisking continuously until smooth.

Place the saucepan over medium heat, stirring constantly.

Continue stirring until the mixture begins to boil.

Once boiling, cook for an additional minute while stirring.

Take the saucepan off the heat and stir in the butter and vanilla extract.

Transfer the pudding to a heatproof bowl and cover with plastic wrap.

Refrigerate for at least 2 hours before serving.