Prepare Your Oven and Tin: Begin by preheating your oven to 175°C (160°C fan/Gas Mark 3). Line a small 20cm x 10cm (8-inch x 4-inch) oven tray with baking parchment, leaving a slight overhang on the sides – this will help you lift the brownies out later. The kitchen should start to feel gently warm, ready for baking.

Melt the Butter: In a medium-sized heatproof bowl, melt the unsalted butter. You can do this in a microwave in 30-second bursts or over a pan of simmering water. The butter should be completely liquid and golden, with a rich, inviting aroma filling your kitchen.

Combine Wet Ingredients: Add the caster sugar and light brown sugar to the melted butter. Whisk them together vigorously for about a minute until the mixture is glossy and smooth. This step is crucial for that fudgy texture, and you'll notice the mixture becoming slightly thicker and lighter in colour. Next, crack in the large egg and add the vanilla extract, whisking again until everything is well combined and the mixture looks pale and frothy.

Incorporate Dry Ingredients: Sift the plain flour, unsweetened cocoa powder, and fine sea salt directly into the wet mixture. Using a rubber spatula, gently fold the dry ingredients into the wet until just combined. Be careful not to overmix; stop as soon as you no longer see streaks of dry flour. The batter will be thick and dark brown, smelling deeply of chocolate.

Add Chocolate and Nuts: Fold in the chocolate chips or chunks and the chopped crunchy nuts. Mix just enough to distribute them evenly throughout the rich, dark batter. You’ll hear a gentle scraping sound as the spatula moves through the thick mixture, and see the glistening chocolate pieces and the rustic texture of the nuts. I stumbled upon this combination by accident one evening, needing a quick dessert, and it's been a hit ever since!

Bake to Perfection: Pour the brownie batter into your prepared oven tray and spread it evenly with the spatula. Place the tray in the preheated oven and bake for 20-25 minutes. The edges will look set and slightly puffed up, while the centre will still have a slight wobble when gently shaken. A skewer inserted into the centre should come out with moist crumbs, not wet batter. The brownies will fill your home with an irresistible, warm chocolate aroma.

Cool and Serve: Once baked, remove the brownies from the oven and let them cool in the tray on a wire cooling rack for at least 30 minutes. This cooling time is essential for them to set and achieve their ultimate fudgy texture. Once cooled, use the parchment paper overhang to lift the brownies out of the tray and slice them into squares. My husband, who's usually picky about baked goods, asked for seconds the first time I made these!