01 -
Cover a casserole dish or baking tray with foil for easy cleanup.
02 -
Toss the cocoa powder and powdered sugar into a bowl. Stir well and sift if it's clumpy.
03 -
Drizzle the milk over the dry mix but don't stir yet. Place the butter chunks on top.
04 -
Microwave on full power for 3–4 minutes until the butter almost melts.
05 -
Quickly stir everything while it's still hot. Once smooth, mix in vanilla and walnuts.
06 -
Pour it into the prepped pan and spread evenly. Let it cool at room temperature until firm.