Line a 20x20 cm (8x8 inch) baking tin with parchment paper.
Sprinkle the bottom evenly with peanuts. Set aside.
Cut the butter into pieces.
Add the butter, sugar, water, and salt to a small saucepan. Heat over medium heat, stirring often, until it is bubbling.
Once bubbling stir occasionally until the mixture reaches a golden brown color around 149 °C (300 °F), which is the hard crack consistency. This usually takes about 8 minutes.
Remove the saucepan from heat and then pour the toffee over the peanuts, spreading it out into a flat layer with a spatula. Set aside and allow it to cool for approximately 2 minutes.
Cut the chocolate into small pieces.
Sprinkle the small chocolate pieces evenly over the hot toffee layer.
Cover with foil for 4 minutes to allow the chocolate to melt.
Cut the peanut into small pieces. Set aside.
Remove the foil and use a spatula to spread the melted chocolate evenly over the toffee to create a thin layer.
Sprinkle the chopped peanuts and a pinch of sea salt over the melted chocolate.
Let it cool down and then refrigerate for at least an hour or until the chocolate is set.
Lift from the baking tin, place it on a wooden board, and remove the parchment paper.
Break the toffee candy into pieces.
Place them on a plate to enjoy.
Notes
Using a Candy Thermometer: To get perfect toffee, I recommend using a candy thermometer. Make sure it reaches 149°C (300°F) for the right crunch. Undercooked toffee will be soft, and overcooked will taste burnt. Temperature Sensitivity: Keep a close eye on the sugar mixture—it’s ready when it turns golden brown. If you wait too long, it can burn and taste bitter. Spreading the Toffee: Work fast when spreading the toffee over the peanuts since it cools quickly. Use a spatula to spread it thin before it hardens. Even Chocolate Melting: After adding chocolate to the hot toffee, cover it with foil and let it sit for 4-5 minutes. This helps the chocolate melt smoothly without overheating. Cooling the Toffee Candy: Let the toffee candy cool completely at room temperature. Putting it in the fridge too soon might make the chocolate separate. Storage: Store the leftover toffee candy in an airtight container at room temperature or in the fridge for up to two weeks. If chilled, let it come to room temp before serving for the best texture.