Line a 12-section bun tray with paper cake cases. Put the chopped chilli, butter, 125 g (4 oz) of the caster sugar, the eggs, flour and baking powder in a bowl and beat with a hand-held electric whisk for about a minute until light and creamy.
Stir in the mango and then divide the cake mixture between the paper cases. Place a halved chilli across the top of each cake.
Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 20 minutes or until risen and just firm to the touch. Transfer to a wire rack to cool.
Put the remaining caster sugar in a small saucepan with the water and heat gently until the sugar has dissolved. Bring to the boil and boil for 3–4 minutes until thickened and syrupy. Stir in 4 tablespoons of the vodka (taking care as the mixture will splutter) and heat until smooth.
Pierce the tops of the cakes with a skewer and drizzle the syrup over. Blend the remaining vodka with the icing sugar to make a thin paste and drizzle over the cakes. Sprinkle with the lime zest.