1. Preheat the oven to 175°C.
2. For the batter: Mix the butter and eggs. In a medium bowl, mix the flour, baking powder, baking soda and salt together. Mix the granulated sugar, milk and lemon peel together. Then mix the butter and eggs into the milk and sugar mixture. Mix the flour into the wet mixture and blend.
3. Place paper cups into a pan, spray with butter baking spray and fill each cup three-quarters full with batter. Drop the coated blueberries on top. Bake for 18 to 20 minutes.
4. For the frosting: Combine the powdered sugar, butter, cream cheese, lemon juice and zest together until light and fluffy. Pipe onto the cupcakes and decorate with lemon peel, blueberries and a mint leaf.