Step 1: Preheat the oven

Preheat your oven to 180°C (350°F). Grease and line the baking tin with parchment paper.

Step 2: Melt chocolate and butter

In a heatproof bowl set over a saucepan of simmering water, melt the chopped chocolate and butter together, stirring occasionally until smooth. Remove from heat and let cool slightly.

Step 3: Mix the wet ingredients

In a large mixing bowl, whisk the eggs and caster sugar together until light and fluffy.

Step 4: Combine dry ingredients

In a separate bowl, sift together the plain flour, cocoa powder, and a pinch of salt.

Step 5: Fold everything together

Gently fold the melted chocolate mixture into the egg and sugar mixture. Gradually add the dry ingredients, folding until just combined. Stir in the chopped nuts.

Step 6: Pour into the tin

Pour the batter into the prepared baking tin, spreading it evenly with a spatula.

Step 7: Bake

Bake in the preheated oven for 25-30 minutes, or until the edges are set but the center is slightly gooey. A skewer inserted into the center should come out with moist crumbs.

Step 8: Cool and slice

Let the brownies cool in the tin for 10-15 minutes before transferring them to a wire rack. Slice into squares or rectangles once fully cooled.