Preheat oven to 350°F.
Line a 9x9” pan with nonstick foil.
Beat butter and both sugars.
Add egg and vanilla.
Add flour, cocoa, baking soda and salt.
Press half into the pan.
Sprinkle on the chips and Oreos.
Drizzle the sweetened condensed milk on top.
Drop rest of dough on top and spread as gently as you can. Not all with be covered.
Bake for about 27-30 minutes.
Cool and cut into squares.