Preheat the oven to 350 degrees.

Grease an eight-by-eight-inch baking pan, and set it aside.

Add the butter to a saucepan, and heat over low heat. When the butter is melted, add the sugar, milk and vanilla, stirring regularly until the sugar is dissolved, and then stir in half of the chocolate chips, stirring until the chocolate is melted.

Meanwhile, add the flour, salt and cocoa powder to a mixing bowl, and stir to combine.

Add in the chocolate mixture, and stir until everything is well combined, and pour the batter into the prepared pan, spreading it out evenly.

Bake for 20 minutes or until the top of the brownies looks set and crackled. (The brownies are meant to stay a bit gooey.)

Set the brownies aside to cool completely.

When they’re cooled, add the rest of the chocolate chips to a small saucepan and heat over low heat, stirring regularly, until the chocolate is melted. Stir in the peanut butter until everything is smooth, and pour it over the brownies, spreading evenly.

Put the brownies in the fridge until the topping sets up, and then store them in an airtight container.