Whisk 2/3 cup sugar, the egg, egg yolks, vanilla extract and cornstarch in a bowl. Cook the milk and 1/3 cup sugar in a saucepan over medium-low heat until foam rises, stirring constantly. Remove from the heat. Temper the eggs with the hot milk mixture, stirring after each addition of the hot milk mixture. Pour the egg mixture into the saucepan. Cook over low heat until the pastry cream reaches 160 degrees F and becomes thick, stirring constantly. Remove from the heat and whisk in the butter. Spread over parchment paper to cool.
Whisk 135 g sugar, the egg, egg yolks, vanilla extract and cornstarch in a bowl. Cook the milk and 65 g sugar in a saucepan over medium-low heat until foam rises, stirring constantly. Remove from the heat. Temper the eggs with the hot milk mixture, stirring after each addition of the hot milk mixture. Pour the egg mixture into the saucepan. Cook over low heat until the pastry cream reaches 70 degrees C and becomes thick, stirring constantly. Remove from the heat and whisk in the butter. Spread over parchment paper to cool.