Preheat the oven to 170°C (150°C fan-forced). Grease or line two baking trays with baking paper or grease two small whoopie pie tins.
Sift together the flour and baking powder in a bowl.
In the bowl of an electric mixer fitted with the paddle attachment, beat the butter (or butter and shortening) until light in colour. Add the sugar slowly. Beat on medium speed until light and fluffy, scraping down the sides of the bowl. Add vanilla essence.
Add the eggs one at a time, beating well for a minute or so after each addition. Add the flour alternately with the buttermilk to the creamed mixture. Mix until just blended. Be careful not to over-mix.
In a small bowl, mix together the milk, baking soda and vinegar. Add this and the hokey pokey pieces to the batter and gently mix.
Using a small ice cream scoop, place scoops of the mixture on the prepared baking trays or spoon mixture into whoopie pie tins.
Bake in the preheated oven for approximately 10-12 minutes or until dry to the touch. Remove to a wire rack to cool completely. Repeat with remaining batter.
Spread buttercream onto half the whoopie pies. Sandwich together with remaining cakes. Roll filled whoopie pies in the chopped hokey pokey or leave plain.
Hokey Pokey: Grease or line a 20 x 30 cm Swiss roll tin with baking paper. Place sugar and golden syrup in a medium saucepan. Heat gently, stirring until the sugar dissolves.
Increase the heat and bring to the boil. Boil for 2 minutes. Stir occasionally, if necessary, to prevent burning. Remove from heat. Add baking soda. Stir quickly until mixture froths up rapidly! Pour into prepared tin immediately. Leave until cold and hard, then break into pieces.
Caramel Buttercream: Put the butter, brown sugar, syrup and cream in a heavy based saucepan. Stir gently over a medium heat until butter has melted, sugar has dissolved and it is well combined. Turn up heat to med-high and without stirring boil for approx. 5 mins. Remove from heat and cool to room temperature.
Pour mixture in the bowl of an electric mixer. Add half of the icing sugar and using a flat beater attachment beat until it is light and fluffy.
add remaining icing sugar gradually and beat until a spreadable consistency is achieved. Add a little more cream if the misture is too dry.
Tip: Remember to give the carton of buttermilk a good shake before measuring out the required amount.
Using dark cane sugar adds to the rich caramel flavour, but brown sugar will work also.