Prepare Your Tray: Preheat your oven to 180°C (160°C fan). Line a 25cm x 38cm (10x15 inch) baking tray with tin foil, making sure the foil goes up the sides. Lightly grease the foil or use non-stick foil. Arrange the saltine crackers in a single, tight layer across the bottom of the tray, breaking some if needed to fill any gaps.

Make the Toffee Mixture: In a medium saucepan, melt the cubed butter and light brown sugar together over a medium heat, stirring until the butter is fully melted and the sugar has begun to dissolve.

Boil the Toffee: Bring the mixture to a rolling boil. Once it's bubbling vigorously, set a timer and let it boil for exactly 3 minutes, stirring constantly with a spatula or wooden spoon to prevent it from catching. The mixture will thicken slightly and turn a deep amber colour.

Pour and Bake: Immediately remove the saucepan from the heat, stir in the vanilla extract (be careful, it will splutter!), and pour the hot toffee evenly over the layer of crackers. I find that pouring in a zigzag motion helps get an even start. Use an offset spatula to quickly spread it to the edges, covering all the crackers.

First Bake: Place the tray in the preheated oven and bake for 5-7 minutes, or until the toffee is bubbling all over.

Add the Chocolate: Remove the tray from the oven and let it stand for 1-2 minutes. Sprinkle the chocolate chips evenly over the hot toffee. Let them sit for 5 minutes; the residual heat will melt them.

Spread and Decorate: Use your offset spatula to spread the melted chocolate into a smooth, even layer. While the chocolate is still wet, sprinkle over your sea salt flakes and any other toppings you're using, like chopped pecans or festive sprinkles.

Cool and Set: Let the tray cool at room temperature for about 20 minutes before transferring it to the fridge to set completely, which will take at least 1 hour.

Break and Serve: Once the chocolate is firm, lift the foil out of the tray. You can either break the toffee into irregular pieces with your hands or use a sharp knife to cut it into neat squares.