• Line a round 8-inch cake pan with parchment paper and spray with non-stick spray. Set aside. Preheat the oven to 375°F.
• Melt ½ cup butter in a large glass microwave-safe bowl in the microwave. Add 1 cup chocolate chips and let sit for 3-4 minutes. Stir until chips melt, adding additional cooking time if needed. Let cool for 5 minutes.
• Whisk ¾ cup sugar and 1 teaspoon vanilla into the melted chocolate mixture. Add 3 large eggs and whisk till well blended. Stir in ½ cup cocoa powder.
• Pour batter into prepared pan and spread evenly with a rubber spatula. Bake at 375°F for 25 minutes or till a toothpick comes out clean.
• Let the cake cool in the pan for about 10 minutes, then invert it onto a wire rack. Immediately flip right-side up onto another cooling rack. Cool completely.

Glaze

• Combine 3 tablespoons butter and ⅔ cup chocolate chips in a glass heatproof bowl. Microwave for 1-3 minutes or till melted, stirring every 30 seconds.
• Spread glaze over the cake. Let sit for several hours till chocolate sets. 
• Serve the cake as is, or with fresh berries, whipped cream, or ice cream.