Prepare Your Baking Arena: Preheat your oven to 175°C (160°C fan/Gas Mark 3). Line a 20x20cm (8x8 inch) square baking tray with parchment paper, leaving an overhang on two sides to easily lift the brownies out later. This small step saves so much cleanup!

Melt and Mix the Base: In a large mixing bowl, combine the melted butter and caster sugar. Whisk them together until the mixture is smooth and slightly glossy. You'll notice a faint sweet aroma filling the air.

Introduce Wet Ingredients: Add the eggs, one at a time, whisking well after each addition until fully incorporated. Stir in the vanilla extract. The mixture should become lighter in colour and thicker, resembling a creamy custard.

Combine Dry Ingredients: In a separate bowl, whisk together the plain flour, cocoa powder, baking powder, and salt. Make sure there are no lumps of cocoa powder; it should be a uniform, deep brown colour.

Fold in the Yoghurt and Dry Mix: Gently fold half of the dry ingredients into the wet mixture until just combined. Then, add the Greek yoghurt and mix until smooth. Finally, fold in the remaining dry ingredients until barely any flour streaks remain. Be careful not to overmix; overmixing can lead to tough brownies. The batter will be thick and rich, a beautiful dark brown. Stir in the dark chocolate chips.

Bake to Perfection: Pour the batter into your prepared baking tray, spreading it evenly with a spatula. Place the tray in the preheated oven and bake for 25-30 minutes. You'll know they’re done when the edges look set and a skewer inserted into the centre comes out with moist crumbs, but not wet batter. The kitchen will smell wonderfully of rich chocolate.

Cool and Slice: Let the brownies cool completely in the tray on a wire rack before lifting them out using the parchment paper overhang. This is crucial for fudgy brownies! Once completely cool, which might take an hour or two, slice them into squares. The texture should be dense and fudgy, with a slight chewiness.