Super silky and delicate butterscotch pudding (a beloved Southern dish) forms the first layer of this delightful tart. It's topped with see-through-thin slices of skin-on, tart Granny Smith apples which provide a protective layer for the hot caramel that tops it all off.
Take extra care with the caramel. It's not difficult to make, but it gets dangerously hot once the sugar turns to caramel and can do serious damage to exposed skin. Use a deep, broad-sided pan and add the cream very gradually, as the sauce will bubble up vigorously as the cream is added.
The pudding, caramel, and pastry shells can be made a full day ahead and the caramel apple tarts can be assembled up to three or four hours before serving. Make sure it's nice and cool when you serve it. Drizzle the plates with leftover caramel sauce. I add just a touch of molasses to the pudding for deeper color and a flavor surprise.
*Note: To blind bake, shape a piece of parchment paper to fit your pan (it should be slightly higher than the pan to hold the pie weights), crumple it up to soften it, and line the tart pans with the paper, covering the dough, and fill almost completely with the weights. You can use dried legumes or beans as well. If using beans, press gently to make sure the beans are evenly distributed.
In a large bowl, whisk together ½ cup of the milk, brown sugar, salt, egg yolks, and cornstarch. Whisk until frothy and well blended. Meanwhile, bring the remaining milk to a boil in a heavy-bottomed, deep saucepan over medium-high heat, watching closely to avoid scalding or spills.
As soon as it just bubbles to a boil, gradually stream the warm milk into the mixture in the bowl. Whisk in until well incorporated. Return the mixture to the same pan and place over medium heat. Whisk vigorously until the pudding starts to set, about 2 minutes. (It should be smooth and firm with a pliable consistency.)
Remove the pan from heat and whisk in the butter, vanilla extract, and molasses. Taste and adjust seasoning (especially the salt). Transfer the pudding into a medium-sized bowl, cover with plastic wrap, and refrigerate until fully cold or overnight.
Place the sugar in a medium-sized, heavy-bottomed pan with high sides. Place over medium heat, gently stirring the sugar to help it melt and caramelize. Once the sugar has completely melted, stop stirring. It will caramelize very quickly, bubbling up a bit in the pan (be careful!).
Once it has turned a luscious caramel color, remove from heat and whisk in the butter until it is melted. Very gradually whisk in the cream. Set aside to cool. When cool enough to handle, either use it to assemble the tart or refrigerate it in a covered container for up to 2 weeks.
Place the butter in the freezer for at least 30 minutes. Remove from the freezer and let stand for 10 minutes.
Meanwhile, combine the flour, sugar, and salt in the bowl of a food processor and pulse 10-12 times (or blend in a bowl with a pastry blender). Cut the butter into ¼-inch cubes and place in the bowl of the food processor. Pulse 40-50 times quickly, just until it resembles the size of very coarse sand or sea salt. (With a pastry blender it takes about the same number of times cutting the butter into the flour.)
Next, trickle the water very slowly into the pastry while pulsing/cutting. At the second the pastry begins to form a big, messy ball, stop. (If it's gummy and sticky, work 2 additional tablespoons flour into the dough.)
Lightly flour your work surface and turn out the pastry. Very quickly shape it into a 2-inch-thick round disk with your hands, scooping up any stray bits and working them into the disk. (It should feel and look like Play-Doh. Look for bits of butter peeking through the pastry — this is a good thing.)
Wrap the pastry in plastic wrap and refrigerate for at least 30 minutes, or better yet, overnight. Lightly flour your work surface and line a baking sheet with parchment paper. Remove the pastry from the refrigerator and split it in ½. Press the top of each pastry 3 times with a horizontal impression of the rolling pin.
Turn them over and roll out the pastry into a large square, ¼-inch thick. Keep the top and bottom of the pastry lightly coated with flour at all times, and turn the pastry intermittently in quarter turns as you work.
Roll gently but quickly, pushing out evenly as you go along. Drape the dough over two 4-by-13-by-1-inch tart pans and roll the pin over the edges of the pan. Chill for at least 20 minutes.
Preheat the oven to 375 degrees.
Remove the tart pans from the refrigerator and blind bake in the oven until golden, about 25 minutes.* Remove the pie weights and brush the sides and top of the tart with the egg wash. Bake until the crust is completely baked and golden, about 15-20 more minutes. Remove from the oven and set aside to cool.
Place equal quantities of the cooled pudding in the bottom of the 2 cooled pastry shells. Using a spatula, even out the pudding so it fully fills the tart shells and is flat and smooth. Arrange the apples along the top of the tarts in 2 rows, forming a kind of layred apple "spine" down the center of each tart.
Top with a generous amount of caramel (about ¾ cup for each tart), brushing it with a pastry brush to evenly disperse and to cover the pudding and apples. Chill the tarts for 2-3 hours before serving. Slice and serve on a plate drizzled with extra caramel sauce.