1. Combine cake mix, butter, egg, sugar and milk in a bowl and mix until smooth. Batter will be thick.

2. Line the bottom and sides of a 9×9 pan with parchment paper.

3. Add a little more than half of the batter to the bottom of the pan and spread evenly. Because the batter is thick, it might help to drop spoonfuls into the pan, then spread.

4. Add the white chocolate chips in an even layer on top of the batter.

5. Pour the sweetened condensed milk in an even layer on top of the white chocolate chips.

6. Drop spoonfuls of the remaining dough on top the sweetened condensed milk, spreading it a bit to mostly cover the other layers.

7. Bake at 350 degrees for 30 minutes.

8. Allow to cool in the pan, then cut into squares. Bars should be good stored in an airtight container for 7-10 days.