Step 1

Preheat oven to 350 degrees. Butter a 9-inch springform pan, line bottom with a round of parchment paper and butter paper.

Step 2

In a large microwave safe bowl, melt chocolate with butter on 50% power in 30 second increments, stirring well between increments until melted and smooth.

Step 3

Whisk in granulated sugar, brown sugar, vanilla and salt until well combined. Add eggs and whisk until well blended.

Step 4

Sift in cocoa powder and whisk until combined. Pour batter into prepared baking dish and spread even. Bake in preheated 25 - 30 minutes.

Step 5

Allow to cool, then cut into slices. If desired top with chocolate ganache, ice cream or whipped cream or powdered sugar. Store cooled cake in an airtight container in refrigerator up to 3 days.