- Step 1
Preheat oven to 180C/160C fan-forced. Grease a 6cm-deep, 20cm round cake pan. Line base with baking paper. Lightly spray baking paper with oil and dust with cocoa.
- Step 2
Process walnuts in a small food processor until they resemble fine breadcrumbs (you'll need 1/2 cup). Melt oil and dark chocolate in a heatproof bowl set over a saucepan of simmering water, stirring until smooth. Remove from heat. Whisk in sugar. Whisk in eggs, 1 at a time. Whisk in extra cocoa, vanilla and salt. Fold in ground walnuts. Spoon batter into prepared pan, spreading to level.
- Step 3
Bake for 35 minutes or until set. Cool in pan. Run a knife around edge to loosen cake. Remove from pan.
- Step 4
Melt extra oil and extra chocolate in a heatproof bowl set over a saucepan of simmering water, stirring until smooth. Cool for 10 minutes. Spread chocolate mixture over cake. Sprinkle with extra walnuts. Cut into wedges. Serve
For more from Martha Stewart, visit marthastewart.com