Melt the butter in the microwave, or in a saucepan on the stovetop.
Pour the melted butter into a large mixing bowl and add the sugar. Stir to combine.
Add the chocolate chips to the melted butter and sugar. Stir gently until the chocolate has melted.
Crack the eggs into a jug then add to the melted butter mix. Use a handheld balloon whisk or wooden spoon and mix until eggs are completely incorporated.
Add the flour and cocoa powder to the brownie mix and stir until just combined. You don’t want to add too much air to the brownie mix or it will lose its gooey texture. Scrape down the bowl and stir again to ensure its evenly mixed.
Line a 13” x 9” (32cm x 22cm) tray with greaseproof paper. Pour in the brownie mix and spread evenly with a spatula or back of a spoon.
Bake in the preheated oven for 35 mins or until the brownie is firm to touch.
Remove from the oven and let cool. Dust with icing sugar if desired and cut into squares to serve.