1. Preheat the oven to 190°C/ fan 170°C / Gas Mark 5.
2. Grease a 24cm square tin with a little butter. Cut a piece of greaseproof paper the same size as the bottom of the tin. Place the paper in the bottom of the tin. This will help you get the brownie out.
3. Place the chocolate and butter in a large bowl, set over a pan of simmering water. Heat gently. Don’t let the water boil rapidly and touch the bottom of the bowl. Stir until the chocolate and butter are melted.
4. Remove from the heat and add the sugar. Stir until well combined. Leave to cool for 5 minutes. Add the eggs and egg yolk one by one, beating well after each egg. You should have a dark glossy mixture. Add the ground almonds, salt and the flour and baking powder. Using a metal tablespoon fold in gently, using a figure of eight movement. Don’t over mix. Finally, fold in the pistachio nuts.
5. Pour the mix into the tin and bake for 20-25 minutes. It should be set, but with a little ‘gooeiness’ in the middle. A good way of testing is to push a skewer into the middle. When you take it out it should be fairly clean, but with a few moist crumbs sticking to it.
6. Leave in the tin to cool, then cut into squares and serve on their own. If they are for dessert, serve with some crème fraîche or double cream on the side.
Recipe courtesy of RSPCA Assured