Preheat your oven to 350°F (175°C) and line a 9×13-inch baking pan with parchment paper.

For the shortbread base, cream together 1 cup (225g) softened butter and 1/2 cup (100g) granulated sugar until light and fluffy.

Mix in 1 tsp vanilla, then gradually fold in 2 cups (250g) flour and 1/4 tsp salt until a soft dough forms.

Press this shortbread dough evenly into the bottom of your prepared pan and bake for about 15–18 minutes, until just set and lightly golden. Let it cool slightly while you make the brownie layer.

Melt 3/4 cup (170g) butter over low heat, then stir in 1 cup (200g) granulated sugar and 3/4 cup (150g) packed brown sugar until smooth.

Beat in the 4 large eggs one at a time, followed by 1 tsp vanilla extract.

Sift together 1/2 cup (50g) cocoa powder, 1 cup (125g) flour, and 1/4 tsp salt, then fold into the wet mixture.

Stir in 1/2 cup (90g) chocolate chips or chunks until distributed, then spread the brownie batter evenly over the cooled shortbread layer.

Bake for 25–30 minutes, until a toothpick inserted comes out with just a few moist crumbs – you want fudgy, not raw.

Heat 1/2 cup (120ml) heavy cream until it’s just about to boil, then pour it over 1 cup (175g) chopped dark or semi-sweet chocolate.

Let it sit for 1–2 minutes, then stir until smooth and glossy. Stir in 1 tsp vanilla extract if using.

Pour the ganache over the warm brownies and spread evenly. Allow to cool completely, then chill for at least an hour to set the ganache before cutting into squares.