Preheat your oven to 180°C (160°C fan) / 350°F. Line a muffin tin with paper liners.

In a large mixing bowl, combine the plain flour, Dutch process cocoa powder, baking powder, baking soda, and salt.

In a separate bowl, whisk together the melted unsalted butter and both sugars. Add the eggs and vanilla extract, mixing until well combined.

Gradually add the dry mixture to the wet ingredients, alternating with the buttermilk, until just combined.

Spoon the batter evenly into the prepared cupcake liners, filling each about two-thirds full. Bake for 18-23 minutes.

Melt the store-bought chewy caramels with thickened cream in a small saucepan over low heat until smooth. Allow to cool slightly.

In a mixing bowl, beat unsalted butter and dark brown sugar until fluffy. Add the caramel mixture, vanilla extract, and icing sugar until smooth.

Once cooled, remove a portion from the center of each cupcake, fill with caramel, and frost with buttercream. Drizzle with chocolate if desired.