Preheat the oven to 180C. Butter and line a metal brownie tray with baking paper.
In a double boiler (a bowl over a saucepan of hot water), melt the chocolate and then add in the butter and stir to combine. Add a pinch of flaked salt to highlight the delicious chocolate. Let cool.
In another bowl, whisk together the eggs and the sugar, until light, fluffy and ribbony. Gradually fold the cooled chocolate mixture into the egg mixture. Fold in the flour. Gently fold in the rhubarb and walnuts. Here some orange zest would be nice, thanks Lynton for the suggestion – next time!
Pour into your prepared brownie tray and smooth down as much as possible to get that nice brownie crust. Bake in preheated 180C for 35 minutes, or until just set.
Allow to cool in the tin and then remove onto a cutting board. Cut into squares and enjoy with friends and family – this is a goodie!