Ingredients

For Brownie mixture

• 110g Dark chocolate
• 225g margarine, softened
• 400g caster sugar or stevia (natural Sweetener)
• 3 eggs
• 2 1/2 teaspoons vanilla extract
• 125g plain flour 
• 225g dark chocolate chips

Topping

• 500g icing sugar
• 2 tablespoons milk, or as needed
• 1 1/2 teaspoons peppermint extract
• 6 drops green food colouring
• 110g butter, softened
• 1 tablespoon vanilla extract

1. Preheat the oven to 180 C. Grease a 20x30cm baking tin.
2. Melt the plain chocolate in the microwave. Stir at 15 second intervals until chocolate is smooth. Allow to cool slightly. Transfer to a large bowl, and stir in the margarine and sugar until smooth. Beat in the eggs one at a time, then stir in the vanilla and dark chocolate chips. Stir in the flour just until blended. Pour the mixture into the prepared tin and spread evenly.
3. Bake in the preheated oven for 20 to 25 minutes or when the edges start to come away from the tin. Remove from the oven and cool in the tin.
4. To make the topping, beat 110g butter with icing sugar in a large bowl. Add milk as needed to get a spreadable consistency. Stir in the peppermint extract and green food colouring. Spread this over the cooled tin of brownies; refrigerate for 30 minutes.