Toffee that is soft?
Basically the hotter you get the sugar, the harder it sets.

One thing you should take note of is the color, the darker the color, the hotter you got it.

Go slowly when melting the sugar, get it to the temperature you want, and then add the rest of the ingredients in. Melting the sugar slower, makes sure that the edges don't get overcooked and burnt.

The more liquids and fats you add, the softer it will set.