Preheat the oven to 180°C, fan 160°C, gas mark 4. In a medium saucepan, melt the butter.
Remove from the heat and stir in the flour, light soft brown sugar, eggs and 4 teaspoons of the lemon extract. Beat with a wooden spoon until smooth.
Pour the mixture into the mini loaf cases and bake for 25 minutes or until golden and risen. Remove from the oven and allow to cool slightly before removing the loaf cases, then set aside.
Meanwhile, make the topping: in a small bowl mix together the icing sugar, caster sugar, 3 teaspoons of the lemon extract and 50ml cold water until the sugar has dissolved.
Pour the syrup over the top of the cakes while they’re still warm and let it drizzle down over the sides. The topping will soak into the cake, but if you want it to penetrate further, pierce the top of the cake with a skewer (taking care not to pierce all the way through).
Scatter the lemon zest over the top of the cakes to decorate. The cakes will keep in an airtight container for 3-4 days.