Combine the milk, vanilla, and sugar and bring to a boil, stirring to dissolve the sugar.
Whip the egg yolks with the second quantity of sugar. Stir in the cornstarch.
Temper the egg mixture with half of the hot milk. Pour this mixture back into the pan with the remaining milk. Return to a boil and boil for 1 minute, until thickened.
Turn out into a bowl and cover the surface with plastic film to prevent a skin from forming. Keep warm while making the Italian meringue.
Boil the sugar and water until the temperature of the syrup reaches 258°F(120°C). Whip the egg whites to firm peaks, then slowly pour the syrup into the whites, whipping constantly. Continue whipping until cool.
Soak the gelatin in cold water and add to the hot pastry cream (a).
Mix until the gelatin is dissolved (b). (If the pastry cream is not warm enough, rewarm it slightly.)
Add one-third of the meringue to the cream and mix quickly to lighten the mixture (c).
Gently fold in the remaining meringue until evenly mixed (d, e).