How to Make It
In a large saucepan, combine the milk, cream, sugar and salt and bring to a boil over moderate heat, stirring to dissolve the sugar. Remove from the heat.
In a medium pot, heat the oil. Add the popcorn kernels, cover and cook over moderate heat until they start popping. Cook, shaking the pot continuously, until the popping has almost stopped, 2 to 3 minutes. Pour all but 1 cup of the popcorn into the cream mixture, cover and let stand for 10 minutes. Reserve the remaining popcorn for garnish.
In a medium bowl, whisk the egg yolks with the cornstarch until smooth. Strain the hot cream mixture into a clean medium saucepan; discard the solids. Bring the cream to a boil over moderate heat. Gradually whisk 1 cup of the hot cream into the egg yolks, then scrape the mixture into the saucepan. Whisk the pudding over moderate heat until it just comes to a boil, about 2 minutes. Stir in the butter and vanilla.
Scrape the pudding into a medium baking dish. Press a piece of plastic wrap directly onto the surface of the pudding and refrigerate until chilled. Spoon the pudding into bowls, sprinkle with the reserved 1 cup of popcorn and serve.