Place the avocado, lime juice, zest and honey in a blender and blitz until completely smooth.
In the bowl of a stand mixer fitted with the whisk attachment, beat the eggs and sugar until very pale and fluffy. The mixture should leave a trail when you draw a figure 8 in the bowl.
Add the avocado mixture and beat quickly. Remove from the mixer.
Sift in the flour, matcha and baking powder and fold gently to form a smooth batter.
Place the madeleine mix in a piping bag and refrigerate for at least 2 hours, or preferably overnight.
Preheat the oven to 200°C, gas mark 6.
Brush madeleine moulds with melted butter.
Pipe the madeleine mixture into each mould and bake for 6-8 minutes.
While the madeleines bake, melt the chocolate in the microwave in 30-second bursts.
Remove the madeleines from the oven and flip onto a cooling rack.
Dip each madeleine halfway into the melted chocolate and sprinkle with the chopped pistachios.