Preheat the oven to 200C/180C fan and line a 12-hole muffin tray with cupcake cases.
Measure all the cake ingredients into a large mixing bowl and beat with a handheld electric whisk for 3 minutes until well combined.
Divide the cake mixture between the 12 cupcake cases and bake for 18-20 minutes. Once cooked, leave to cool for 5 minutes in the tin before transferring to a cooling rack to cool completely.
While your cupcakes are cooking, make your filling. In a small saucepan, warm the caramel over a medium heat. Once it begins to boil, lower the heat and simmer for 2 minutes. Add the Baileys Chocolate Luxe and continue to simmer for 1-2 minutes, stirring constantly. Take off the heat and pour the caramel mixture into a heatproof bowl and set aside to cool at room temperature.
Once the cupcakes have cooled, use a small knife to cut out a small cone in the centre of the cupcake. Spoon the filling into the hole in the cake.
Beat the butter in a freestanding mixer with a whisk attachment on a medium speed for 2-3 minutes. Add the Baileys Chocolate Luxe and beat for a further 1 minute until combined. Add in the icing sugar and whisk on a low speed for 1 minute and then increase to a medium speed for 4 minutes, until the icing is light and fluffy. Add the boiling water and beat for 1 minute until combined and smooth. Transfer the buttercream into a piping bag fitted with a 1cm round nozzle.
Melt the chocolate together with the oil in a bowl over the same simmering pan, stirring until melted and combined. Pour the chocolate mix into a glass or mug just wider than the cupcake.
Pipe the buttercream in a high swirl on top of the cupcake and then, holding the base of the cupcake upside down, dip the topping into the chocolate. Gently shake off any excess chocolate and then transfer the cupcake to a board or wire rack. Decorate with gold dust, gold covered cherries or sprinkles immediately. Repeat with all the cupcakes.