Preheat the oven to 180C/160C Fan/350F/Gas 4. Line an 8x8-inch square baking pan with parchment paper, and set aside.
Place the butter, sugar, cocoa powder, and salt into a large microwave-safe bowl, and heat for 30 seconds.
Stir well, then continue heating in 30 second intervals (stirring after each one) until combined and very warm/hot to the touch.
Add the eggs and vanilla, and mix well until combined.
Fold in the flour until fully combined, then gently fold in the chocolate chips. Be sure not to let them ALL melt into the warm batter.
Pour the batter into the prepared pan and spread out evenly.
Bake for 30 - 35 minutes, or until the centre is no longer jiggly and a toothpick/cake tester inserted comes out almost clean with a few moist crumbs.
Allow to cool completely in the pan on a wire rack before cutting into bars.
TIP: To speed up the cooling time (and for cleaner, neater slices), place the pan in the freezer for 1 hour.
Video
Notes
Brownies stay fresh stored in an airtight container at room temperature or in the fridge for up to 1 week. They also freeze well for up to 3 months. Thaw overnight in the fridge before serving.