• Preheat your oven to 350°F (175°C) and line a cupcake pan with paper liners; set aside. In a medium bowl, whisk together the flour, baking powder, and salt until well combined. In a separate large mixing bowl, cream the butter and sugar together until the mixture is light, fluffy, and pale in color. Add the eggs one at a time, beating well after each addition, then mix in the vanilla extract. Alternately add the flour mixture and the milk to the creamed mixture, starting and ending with the flour. Be sure to scrape down the sides of the bowl and mix just until everything is combined—avoid overmixing. Divide the batter evenly among the cupcake liners, filling each about three-quarters full. Bake for approximately 20 minutes, or until the tops spring back when lightly touched. Remove from the oven and let cool in the pan for 5 minutes, then transfer to a wire rack to cool completely. Once cooled, use a small paring knife to remove a bit from the center of each cupcake and fill the cavity with a small dollop of salted caramel sauce.

For the Frosting:

• Set a heatproof bowl over a pot of gently simmering water to create a double boiler. Combine the egg whites, granulated sugar, and salt in the bowl and whisk continuously until the sugar is fully dissolved and the mixture reaches 160°F (70°C), about 5 minutes. Stir slowly and steadily—be careful not to scramble the eggs. Once heated, transfer the mixture to the bowl of a stand mixer fitted with the whisk attachment and beat on high speed until stiff peaks form and the mixture has cooled to room temperature, around 5 minutes. Reduce the speed to medium and begin adding the softened butter, one piece at a time, allowing each addition to fully incorporate before adding the next. If the mixture appears to curdle partway through, don't worry—just keep beating and continue adding butter; it will come together. Switch to the paddle attachment and mix in ¾ cup of the salted caramel sauce, beating until the buttercream is smooth, silky, and well blended, about 1 minute. Pipe or spread the caramel buttercream onto the cooled cupcakes, then drizzle with the remaining caramel sauce and finish with a sprinkle of sea salt.