Method
1. Add heavy cream and unsalted butter to a clean saucepan
2. Heat until just boiling - low heat
3. Add dark chocolate to a clean medium bowl
4. Pour cream into the chocolate and mix gently until completely melted
5. Chill in fridge - 1 hr
6. Pre-heat oven - 174°C
7. Grease a clean square pan
8. Add unsalted butter and dark chocolate to a clean small glass bowl
9. Melt in microwave then set aside - low heat
10. Add light brown sugar, granulated sugar and egg yolk to a clean large mixing bowl
11. Whisk until thick - 5 min
12. Mix chocolate mixture into the sugar-egg mixture then set aside
13. Add all purpose flour, cocoa powder and walnuts to a clean medium bowl
14. Mix dry ingredients into batter gently then set aside
15. Add egg white to a clean large mixing bowl
16. Beat until stiff peaks form
17. Fold egg whites into batter gently until just combined
18. Transfer batter to square pan
19. Bake - 20 min, 174°C
20. Let cool completely
21. Spread glaze over the brownies
22. Sift cocoa powder onto the brownies
23. Cut into squares