For the cookie crust

1. Mix cookie crumbs, butter, and salt in a medium bowl until butter is evenly distributed and mixture looks like wet sand. Press about 2 tablespoons of the cookie mixture onto the bottom of eight (8-ounce) mason jars or ramekins.

For the caramel pudding

1. In a small bowl, whisk 1/2 cup of the milk with the cornstarch, vanilla and salt until smooth. Set aside.
2. In a large saucepan, combine the sugar with the water and bring to a boil. Cook over moderately high heat, undisturbed, until the sugar mixture turns a deep amber color, about 8 minutes. Remove from heat. Very gradually whisk in the remaining 3 1/2 cups of milk, 1/4 cup at a time. The mixture will bubble up when you first add the milk but will settle as you whisk it. Whisk the pudding over moderate heat until the caramel has dissolved into the milk. Bring mixture to a simmer. Cook the pudding over moderately low heat, gently whisking occasionally, until the mixture thickens slightly and deepens in color, about 10 minutes. Remove from heat.
3. Stir the cornstarch mixture again in case it has separated. Gradually whisk the cornstarch mixture into the pudding mixture. Cook the pudding over moderate heat, stirring, until the pudding is very thick, about 1 minute. Pour the pudding into prepared jars (about 1/2 cup per jar). Refrigerate until the pudding is set, 4-5 hours.

For the salted caramel sauce

1. Stir sugar, corn syrup, and water in a deep medium saucepan over low heat. Increase heat to medium; cover pan and cook 4 minutes. Uncover; increase heat to moderately high. Let the sugar mixture boil, undisturbed, until it turns golden brown to deep amber in color, about 6 minutes. Remove from heat. Slowly whisk in cream, 1/4 cup at a time. The mixture will bubble up when you first add the cream but will settle as you whisk it. Whisk in butter and salt. Cool completely.

For serving

1. Whip cream with sugar until soft peaks form. Set aside.
2. Remove pudding jars from the refrigerator. Spoon 2 tablespoons caramel sauce into each jar. Top with whipped cream and sprinkle with cookie crumbs.