3/4 cup semisweet chocolate chips, melted and cooled
2 large eggs, lightly beaten
1-1/2 cups semisweet chocolate chips
1/2 cup heavy whipping cream
1 teaspoon vanilla extract
Preheat oven to 350°. Line a 13×9-in. pan with foil, letting ends extend up sides; grease foil. In a microwave, melt butter in a large microwave-safe bowl. Stir in sugar, cocoa and vanilla. Add egg; blend well. Add flour, baking powder and salt; stir just until combined. Spread into a thin layer into prepared pan. Bake until top appears dry, 6-8 minutes.
Meanwhile, in a large bowl, beat cream cheese, sugar and vanilla until smooth. Beat in cooled chocolate chips. Add eggs; beat on low speed just until combined. Spread over brownie layer. Bake until filling is set, 25-30 minutes. Cool 10 minutes on a wire rack.
For ganache, place chocolate chips in a small bowl. In a saucepan, bring cream just to a boil. Pour over chocolate; let stand 5 minutes. Stir with a whisk until smooth. Stir in vanilla; cool slightly, stirring occasionally. Pour over cheesecake layer; cool in pan on a wire rack 1 hour. Refrigerate at least 2 hours. Lifting with foil, remove brownies from pan. Cut into bars.