Combine the flour, cocoa powder, sugar, and salt. Mix well and then set aside.
Using a different bowl, combine the eggs, vegetable oil, and vanilla extract. Whisk until all the ingredients are incorporated.
Fold-in the dry ingredients and mix until everything is well distributed.
Preheat oven to 350 degrees Fahrenheit.
Arrange the mixture in a baking pan.
Bake for 20 minutes, or until it passes the toothpick test
Melt the chocolate chips in a saucepan and then pour-in the condensed milk and vanilla extract. Mix well.
Remove the brownies from the oven and then spread the chocolate mixture over. Sprinkle the top with chopped walnuts. Let cool in room temperature and then refrigerate for a couple of hours.
Serve. Share and enjoy!