Preheat the oven to 350-degrees and grease a 9" x 13" casserole baking dish.
In a medium-sized bowl, add the 1-1/2 cups flour, unsweetened cocoa, and the salt and sift together. Set aside.
Add the melted butter and sugar to a large bowl and mix together.
Now, add the eggs, one-at-a-time and mix well. Add the vanilla extract and mix.
Next, add the flour mixture to the batter and mix.
In a small bowl, add the chocolate chips and 1 teaspoon of flour and toss, then add the chips to the brownie batter and mix well.
Spread half of the batter into the greased 9" x 13" dish.
In a medium-sized bowl, add the sweetened condensed milk and peanut butter and mix. Spread over the brownie batter.
Spread the remainder of the brownie batter over the sweetened condensed milk.
Bake for 45 to 50 minutes or until a cake tester comes out mostly clean.
Allow the brownies to cool for at least 45 to 60 minutes.