Preheat and prepare: Set your oven to 180°C (160°C fan) and line a 20cm square baking tin with baking parchment. Leave a little overhang on two sides — this will become your handle for lifting the blondies out later.

Melt the butter: Place the 115g unsalted butter in a large microwave-safe bowl and heat in 20-second bursts until fully melted. You’ll know it’s ready when you see a pool of clear, golden liquid with no solid pieces remaining. Give it a quick swirl to check.

Stir in the sugar: Add the 200g light brown sugar to the melted butter and stir vigorously with a wooden spoon until the mixture looks like wet sand — it should be glossy and smell wonderfully sweet. The sugar needs to be fully incorporated so there are no gritty lumps.

Add the eggs and vanilla: Crack in the whole egg and the extra yolk, then add the 2 teaspoons of vanilla extract. Whisk by hand until the batter is smooth, pale, and slightly thickened — this should take about 30 seconds. You’ll notice the mixture has become noticeably lighter in colour and feels silky when you lift the spoon.

Fold in the dry ingredients: Sift the 190g plain flour, ½ teaspoon bicarbonate of soda, and ½ teaspoon salt directly into the bowl. Fold gently with a spatula until just combined. Stop the moment you no longer see streaks of flour — over-mixing will make the blondies tough and cakey rather than chewy. The batter will be thick and slightly tacky.

Add the chocolate chips: Tip in the 200g dark chocolate chips and fold them through with a few swift strokes. You want them evenly distributed, with each spoonful promising a little pocket of melted chocolate. The batter will now look studded with dark speckles against the golden dough.

Bake to perfection: Scrape the batter into your prepared tin and spread it into an even layer using the back of your spatula. Bake for 22-25 minutes. The edges should be a deep, golden brown and pulling away from the sides of the tin, while the centre will still look slightly soft and underdone. The top should be crackled and shiny — that’s the sign of a properly baked blondie. A skewer inserted into the centre should come out with a few moist crumbs attached, not wet batter.

Cool and slice: Place the tin on a wire rack and let the blondies cool completely in the tin — this is crucial. The residual heat continues to set the centre, giving you that signature chewy texture. Once cool, lift the parchment to remove the slab, then slice into 16 squares with a sharp knife. You’ll hear a slight crackle as the knife cuts through the sugary top.