Combine 1/4 cup whole milk and cornstarch in a bowl, stirring well with a whisk. Combine remaining 3/4 cup whole milk and 2% milk in a medium saucepan over medium heat, and bring to a simmer.
Add 1 cup maple sugar, vanilla extract, salt and 2 egg yolks to cornstarch mixture and stir well with a whisk.
Gradually add warm milk to the sugar mixture, stirring constantly with a whisk.
Return the mixture to the saucepan and cook over medium heat until mixture begins to boil, stirring constantly with a whisk. Cook for 1 minute, or until mixture is thick, stirring constantly.
Remove from heat. Add 1 Tablespoons butter and stir until butter melts.
Place the pan in a large ice-filled bowl for 6 minutes, or until the pudding cools, stirring occasionally.
Cover surface with plastic wrap. Chill a least 3 hours before serving.