Step 1: Prepare the Baking Tray

Grease a large baking tray or line it with parchment paper. You’ll need this ready for when the brittle mixture is done cooking.

Step 2: Cook the Sugar Syrup

In a large, heavy-bottomed saucepan, combine the sugar, water, and golden syrup. Place the pan over medium heat and stir gently until the sugar has completely dissolved. Once dissolved, stop stirring and bring the mixture to a boil.

Step 3: Add the Peanuts

Let the sugar mixture cook and bubble until it turns a golden amber color, which should take about 10-15 minutes. You can use a candy thermometer if you have one — the mixture should reach around 150°C (300°F), also known as the “hard crack” stage. Once it reaches this stage, quickly stir in the roasted peanuts.

Step 4: Add the Butter and Vanilla (Optional)

If you’re using butter for extra richness, stir it in along with the vanilla extract at this stage. This will give the brittle a deeper, more complex flavor.

Step 5: Add the Baking Soda

Remove the saucepan from the heat and immediately stir in the baking soda. The mixture will bubble up slightly and lighten in color, giving the brittle a lighter, airy texture.

Step 6: Pour and Spread the Brittle

Quickly pour the hot mixture onto the prepared baking tray. Use a spatula to spread it out as evenly and thinly as possible. Be careful — the mixture will be extremely hot!

Step 7: Cool and Break the Brittle

Let the peanut brittle cool completely, which will take about 30 minutes. Once it’s hardened, break it into pieces by hand or using a rolling pin.