Place chocolate and butter into a large heat-proof microwave-safe bowl and press the MELT CHOCOLATE button on the shortcuts panel and turn to amount to 200g. Press start button to commence melting. Once finished, carefully take out and stir until smooth and well combined. Cool slightly

Beat in sugar and mix well

Whisk eggs and mix through

Sift flour, baking powder and cocoa together and fold through chocolate mixture

Fold through walnuts and mix until just combined

Pour into the greased crisper tray. Smooth the surface with a spatula and elevate crisper tray and place on turntable

Select 50% power and dial up 15 minutes; press START/+30SEC button. Cook until just cooked through; centre will be soft. Select Grill Only and dial up 5 min. Press start button

Remove and cool completely before cutting into squares. Dust with cocoa powder