Preheat oven to 350F.

Butter and flour a 12-cup Bundt pan. In a small mixing bowl, using an electric mixer, beat cream cheese and sugar until smooth. Add egg and vanilla; beat until blended and set aside.

Prepare cake as label directs; fold in chocolate morsels. Pour chocolate batter into prepared pan; evenly cover with cream cheese mixture.

Bake until a toothpick inserted in the center of the cake comes out clean, 45 to 55 minutes. Cool on a wire rack 25 minutes. Remove from pan; cool completely. Dust with powdered sugar.