In a medium-sized bowl, mix butter, sugar, and salt until light and fluffy.
Beat the egg into the butter/sugar mixture.
Alternately mix in the flour and the milk mixture, scraping down sides of bowl between each addition.
Mix until the mixture forms a smooth ball (If you have a stand mixer, use a dough hook and beat dough on medium speed for 7 to 10 minutes.)
Line cupcake tins with 18 liners.
Divide crust evenly (or as close as you can get) between the liners - pressing it with your fingertips into the bottom of the liners.
Cover tins with plastic wrap or a towel, put in a warm place, and allow to rise until doubled, 2 1/2 to 3 hours.
Gooey topping instructions
In a small bowl, whisk corn syrup with water and vanilla.
In a medium-sized bowl, mix butter, sugar and 1/2 teaspoon salt until light and fluffy.
Beat the egg into the butter/sugar mixture.
Alternately add popcorn flour and corn syrup mixture, scraping down sides of bowl between each addition.
Spoon topping evenly over risen crusts.
Lightly sprinkle the top of each cupcake with salt.
Bake at 350 F for exactly 20 minutes. Note that you can't use the standard toothpick method to tell if they are done because they are supposed to be gooey. I found that if I baked the cupcakes more than 20 minutes, they overflowed.