Best Chocolate Brownie

• 10 secon sour cream
• 3 eggs
• 2 cake (square pan)
• 1 coarsely (chopped)
• 280 gr bittersweet chocolate
• 150 gr granulated sugar
• 60 ml sour cream
• 34 gr butter (unsalted)
• 32 gr flour
• 12 gr unsweetened cocoa