Preheat your oven to 350°F (175°C). Line a muffin tin with cupcake liners and set aside.

In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt. Set aside.

In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.

Beat in the eggs, one at a time, mixing well after each addition. Then, add the dissolved espresso powder mixture and vanilla extract, and mix until well combined.

Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix until just combined, being careful not to overmix.

Divide the batter evenly among the prepared cupcake liners, filling each about 2/3 full.

Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center of a cupcake comes out clean.

Remove the cupcakes from the oven and allow them to cool in the muffin tin for a few minutes before transferring them to a wire rack to cool completely.

While the cupcakes are cooling, prepare the salted caramel buttercream. In a mixing bowl, beat the softened butter until creamy. Gradually add the powdered sugar, mixing until smooth.

Add the salted caramel sauce, vanilla extract, and a pinch of salt to the buttercream, and beat until well combined and fluffy. Adjust the consistency by adding more powdered sugar if needed.

Once the cupcakes are completely cooled, frost them with the salted caramel buttercream using a piping bag or an offset spatula.

If desired, drizzle the cooled salted caramel sauce over the frosted cupcakes for garnish.

Serve and enjoy these delicious chocolate espresso cupcakes with salted caramel buttercream as a decadent treat!