Speedy one-pan brownies

1 Preheat the oven to 190˚C, gas mark 5. Grease a 20cm square cake tin and line with baking parchment. In a large heavy-based pan, melt the butter and dark chocolate over a low-medium heat. Take off the heat, add the sugar and eggs, and use a wooden spoon to stir together. Once everything is incorporated, stir in the flour. Pour the chocolate mixture into the lined tin. Bake for 30 minutes, until just set with a slight wobble (don’t test with a skewer). Leave in the tin to cool completely before lifting out and cutting into squares. 

2 To make the drizzle, put the white chocolate in a heatproof bowl and melt over a pan of barely simmering water, ensuring the bowl is not touching the water. Once almost melted, take the pan off the hob and stir to finish melting the chocolate. Use a spoon to drizzle over the brownies. Keep in the fridge for up to 4 days, if not eating straight away.