Raspberry lamington cookies

Ingredients

• 250 grams butter, softened
• 1 cup caster sugar
• 1 egg
• 1 teaspoon pure vanilla extract
• 1/3 cup sour cream
• 3 cups plain flour, sifted
• 1 1/2 teaspoon baking powder, sifted
• 1/4 teaspoon salt
• 1 cup thread coconut, to coat
• 1/2 cup mascarpone, to serve
• 1/4 cup raspberry jam, to serve
• Raspberry icing
• 3 cups icing sugar, sifted
• 1/2 teaspoon raspberry essence
• 3 - 4 tbsp milk
• 1/4 - 1/2 tsp pink food colouring