Preheat the oven to 180°C/ 160°C fan/ gas mark 4/ 350°F
Line the tin with magic liner or paper liner
Crush the rice crispies - easiest in a bag with a rolling pin
For the base:
Melt the butter in the microwave or in a saucepan over a LOW heat and stir in the rest of the ingredients for the base(Crushed rice crispies, sugar, flour, cocoa, baking powder, salt)
Press into the prepared tin and cook for 20 minutes. Cool in the tin
For the mint icing:
Mix the icing sugar and water so that it is still stiff but can be spread easily. No need to sieve unless the sugar is very lumpy.Start with 35ml water and add more if needed
Add peppermint extract to taste and green colouring to get the colour you want and mix in well
Pour the icing onto the base, spread evenly with a knife, and leave to cool slightly.
For the chocolate topping:
Put the chocolate in a small basin and EITHER:Melt in the microwave in 30-second bursts on high power, stirring in between. Once the chocolate begins to melt, keep the time down. If you overheat it, the chocolate will be ruined. OR Put the basin over a saucepan of hot water. Don’t let the water boil. Keep stirring
When the chocolate has melted, pour over the icing and spread evenly with a knife
Leave to cool, then cut into squares.
Notes
Store Chocolate Mint Crispies in an airtight tin for up to a week - longer if they're in the fridge.