• Gather all the ingredients. Since candy making is like chemistry, I do not recommend substituting ingredients (except for the type of nuts) or changing the portion of ingredients. Once you made this recipe several times and feel confident, you can double the recipe. However, I do not recommend tripling the recipe.
  

Before You Start (Caution)

• Butter separation is a common issue for toffee making. Fortunately, it has never happened to me with this recipe (the recipe source in the post and Notes), but remember to follow the instructions precisely when making toffee. 1) Use a heavy-bottomed pot as I mentioned in the post. If your pot is too thin, hot spots on a pot can cause separation. 2) Use a long wooden spoon. It's a traditional tool that works the best. I heard different materials could contribute to butter separation. A long utensil helps not to burn your hand. 3) Avoid rapid temperature changes. Do not heat it up and down during cooking or move it around on the burner too much. 4) Use medium-high heat all the way. 5) Stir constantly. You are going to need to stand by the stove while making toffee.

To Prepare Walnuts and Almonds

• Finely chop raw walnuts and set aside.
  
• Place the almonds in a single layer on a baking sheet lined with parchment paper. Almonds should be over an area measuring about 10 inches x 7 inches (25 cm x 18 cm). Optionally you could bake the almonds in the preheated oven at 300ºF (150ºC) for 10-15 minutes to bring out more flavors.
  

To Prepare Chocolate

• Melt semi-sweet or bittersweet chocolate chips over a double boiler until the chocolate is soft enough to stir smoothly. Turn off the heat and keep it warm while making toffee. Alternatively, you can melt the chocolate in the microwave for about 1 to 1.5 minutes. Remove from the microwave and stir. Repeat heating at shorter intervals, 15 to 20 seconds, stirring in between, until the chocolate is completely melted and has a smooth consistency.
  

To Make Toffee

• In a heavy-bottomed, 2-quart saucepan, add unsalted butter, granulated sugar, kosher salt, and vanilla extract. If you are using a candy thermometer, attach it to the saucepan.
  
• Cook over medium-high heat, stirring with a clean, dry long wooden spoon until the butter is melted. Make sure the butter and sugar are melting together. If the two elements melt unevenly, it can result in separation. 
  
• Once the butter is melted, set the timer for 5 minutes. Bring the mixture to a steady boil (not a rolling boil) and cook, stirring constantly, until the toffee is the color of whole raw almonds. As the temperature of the pan and mixture rises you will notice the mixture will bubble and foam as the water boils off and the color darkens around the edges where the mixture touches the pan. Stir the sides and bottom of the pan to even out the mixture temperature. Depending on your heat, it might take 5 to 7 minutes.
  
• When the water has boiled off, the volume will collapse and thicken and the temperature of the mixture will rise quickly. As the mixture heats up, the color of the mixture changes drastically, especially during the final minute. When the candy is the color of raw almonds (or some calls it the color of a brown paper bag) or your candy thermometer registers 290-300 ºF (143-150 ºC), turn off the heat.
  
• ⚠ If the mixture separates while it is cooking, there is a chance you can save it. Although I had never experienced butter separation before, I learned from my research that sometimes separated toffee can be saved by removing the saucepan from the heat and stirring constantly until it comes back together into a smooth mixture. Gradually return it to the heat, stirring constantly. You can also try adding 1-2 Tbsp of very hot water to the toffee to help it come together (up to 4 Tbsp).
• Immediately pour the toffee over almonds, covering all nuts and smoothing into an even layer. Do not scrape the pan. Let the toffee cool for a few minutes. Keep the toffee saucepan for delicious hot caramel milk (see the instructions below).
  
• ⚠ If you have already poured the toffee out to cool by the time it separates, the toffee is unfortunately too far gone to save. However, once it solidifies, you can try wiping off the excess oil and crush the toffee to sprinkle over ice cream.
• Spread the chocolate over slightly cooled toffee.
  
• Sprinkle with walnuts and let cool until chocolate is firm, about 2 hours (or once the toffee is cool down, refrigerate for 20 minutes to speed up the process).
  
• Once set, cut with a sharp knife or break into bite-size pieces.
  

Storage

• Store toffee in an airtight container at room temperature in a cool, dry place for up to 2 weeks, in the refrigerator for up to 3 months. For longer storage, freeze up to 6 months and thaw overnight in the refrigerator before serving.

To Make Hot Caramel Milk

• Add a small amount of milk to the pot with caramel leftover in it. Scrape off the sides and bottom with a silicone spatula or wooden spoon. Once the pot is clean, add more milk to adjust the sweetness. Enjoy hot/warm!