How to Make It
Preheat the oven to 375°. Line a baking sheet with parchment paper. In a medium bowl, combine the flour with the baking powder, sugar and salt. Using a pastry blender or 2 knives, cut in the butter until it is the size of small peas. Make a well in the center.
In a small bowl, whisk 1/2 cup of the cream with the egg and pour into the well in the dry ingredients. Stir until a shaggy dough forms. Turn the dough out onto a lightly floured surface and knead 2 or 3 times, or just until the dough comes together.
Roll out the dough 3/4 inch thick. Using a 2 1/2-inch biscuit cutter, stamp out 6 rounds as close together as possible. Pat the scraps together, re-roll and cut out 2 more rounds. Transfer the shortcakes to the prepared baking sheet.
In a small bowl, whisk the remaining 1 tablespoon of cream with the dulce de leche. Brush the tops of the shortcakes with the glaze and bake for 18 minutes, or until risen and golden. Transfer the shortcakes to a rack to cool.
Fill a very large bowl with ice. In a large bowl, combine the heavy cream with 1/2 cup of the dulce de leche. Set the bowl over the ice and beat the cream until soft peaks form. Refrigerate the cream.
In a large skillet, melt the butter. Add the pineapple rings in a single layer and cook over high heat, turning once, until lightly browned, about 5 minutes. Add the remaining 1/4 cup of dulce de leche and the pineapple juice and cook until bubbling, 2 to 3 minutes longer.
Split the shortcakes horizontally and set the bottom halves on plates. Spoon the pineapples rings and sauce over the cakes. Top with the whipped cream, then the shortcake tops, and serve.