Have your candy thermometer nearby before you start and have the nuts weighed out and ready to be added. Break up the chocolate and add to a microwave safe bowl and set aside to melt later.
Prepare a half sheet baking pan by lining it with parchment paper or a silicon baking mat.
Have some oven gloves nearby ready to grab when you need them, as well as a side plate to place your candy thermometer once you remove it from the pot.
Add the vegan butter, sugar, syrup, soy milk and salt to a large heavy bottomed pot and turn the heat to medium/high.
Stir constantly as the butter and sugar melts. The sugar will make a scraping sound as you stir it in the pot, when the scraping sound disappears your sugar is properly melted.
When your ingredients are melted, add in your sugar thermometer.
Keep stirring as it comes to a boil and keep stirring all the way through until it registers 'soft crack stage' or 285°F (137°C).
Immediately turn off the heat, remove the candy thermometer and then grab your oven gloves (the pot handles will be hot) before lifting up the pot and pouring the toffee out onto your parchment lined baking tray.
Use a spoon to spread it out a little (very quickly).
Then grab your mixed nuts and throw those over the top of the hot toffee, using the spoon again to press them down into the toffee.
Quickly melt your chocolate in the microwave by microwaving for 30-second intervals and then bringing it out to stir, then putting it back in for another 30-seconds until melted.
Pour out over the top of the toffee and nuts and smooth down with a knife.
Sprinkle some crushed mixed nuts over the top of the melted chocolate.
Place the whole tray into the fridge for a few hours for the toffee to set.
Break into pieces.
Keep stored in an airtight container in the fridge where it will stay good for weeks!