Preheat oven to 350ºF. Prepare 9 in. x 9 in. square pan with vegetable pan spray.

Combine butter and 1/4 cup chocolate chunks in medium microwave-safe container and heat at 30 second intervals until evenly melted, stirring between each. Add vegetable oil and 1 cup granulated sugar and stir thoroughly. Add cocoa powder, 1-1/2 teaspoons vanilla, icing color, vinegar and salt, stirring after each addition. When fully combined, alternately stir in 2 eggs and flour. Fold in remaining 1/2 cup chocolate chunks. Reserve 1/4 cup batter for topping, and pour remaining batter into prepared pan.

For cream cheese layer, beat softened cream cheese and 1/4 cup sugar with electric mixer on medium speed until smooth. Beat in 1/2 teaspoon vanilla. Add 1 egg and beat at medium speed for 2 minutes until smooth. Drop cream cheese mixture by 1/4 cupfuls on top of brownie mixture, then top with remaining brownie batter by tablespoon drops. Use spatula to swirl together batters.

Bake for 33-35 minutes. Allow to cool completely on cooling grid before cutting.