In a large mixing bowl, combine the melted butter and powdered sugar. Whisk together until the mixture becomes lighter in color and slightly fluffy. Add the eggs one at a time, mixing thoroughly after each addition. Incorporate the curd, honey, and vanilla extract, stirring until the mixture is smooth and uniform.

In a separate bowl, sift together the refined flour, baking powder, and salt. Stir in the mandarin zest to evenly distribute its natural oils throughout the flour mixture.

Gradually add the dry ingredients to the wet ingredients in batches, alternating with the milk. Stir gently after each addition to prevent overmixing. Once all ingredients are combined, add the orange juice and give the batter a final gentle mix.

Preheat the oven to 180°C (350°F). Line a cupcake pan with paper liners. Spoon the batter into each liner, filling them approximately two-thirds full. Bake for 18–20 minutes, or until a toothpick inserted into the center comes out clean. Allow the cupcakes to cool completely on a wire rack before frosting.

In a mixing bowl, beat the softened butter at high speed for 4 to 5 minutes until it becomes light and creamy. Add the vanilla extract and mix to incorporate. Gradually add the powdered sugar in small increments, continuing to beat until the desired consistency is achieved and the frosting can hold its shape.

Once the cupcakes are completely cool, apply the buttercream frosting using a piping bag or a spatula. Serve immediately or store as needed.