Preheat your oven to 160ºC (fan) and line a 9-inch (23 cm) square baking pan with grease-proof/ parchment paper.
In a medium mixing bowl, melt the butter in the microwave.
Add the eggs, vanilla extract, and caster sugar to the melted butter. Mix well.
Sift in the plain flour and cocoa powder.
Add the instant coffee powder. Gently combine the dry ingredients into the egg mixture using a large spoon until just combined. Do not overmix.
Pour in the chocolate chips and stir gently once or twice to distribute them throughout the batter.
Spread the brownie batter evenly into a baking tin.
Bake for about 18 minutes, until the top is set and the inside is still slightly fudgy.
Allow the brownies to cool in the pan for about 30 minutes before cutting them into 16 squares with a sharp knife.