Step 1: Prepare the Pan
Preheat the oven to 175°C (350°F).
Line an 8-inch square baking pan with parchment paper, leaving some overhang for easy removal.
Step 2: Melt the Chocolate
In a heatproof bowl, combine the butter, chopped chocolate, and cocoa powder.
Place the bowl over a pot of simmering water, ensuring the bowl does not touch the water.
Stir frequently until melted and smooth.
Remove from heat and let cool slightly.
Step 3: Make the Batter
In a separate mixing bowl, whisk together the sugar and hot water until the sugar dissolves completely.
Stir in the vanilla extract.
Pour in the melted chocolate mixture and whisk until smooth.
Add the yoghurt and mix until fully incorporated.
Sift in the flour, cornstarch, and salt.
Fold gently until a smooth batter forms with no flour lumps remaining.
Step 4: Bake the Brownies
Pour the batter into the prepared pan and smooth the top evenly.
Bake for 25–30 minutes, or until a crust forms on top and a toothpick inserted in the center comes out with moist crumbs.
Avoid overbaking, as this can make the brownies dry. Begin checking around 20 minutes if your oven runs hot.
Step 5: Cool and Slice
Allow the brownies to cool completely in the pan.
Lift them out using the parchment paper overhang.
Slice into 16 equal squares, wiping the knife clean between cuts for neat edges.
For the best texture, let the brownies rest overnight before slicing.