To get started grease or spray a pan. Using parchment paper you spray or butter it.
Pour butter into a heavy saucepan and add sugar.
When butter is melted the sugar starts to turn colors. From light tan to brown. When the toffee is brown your candy thermometer should read 290 degrees. Take off heat. The recipe says 300 degrees, but I have found that 300 degrees is to hot. It turns the toffee burnt and bitter.
Pour the toffee into the pan. It's very hot, so be very careful. Let cool.
When the chocolate is cooled add your dark or milk chocolate chips it melts faster. Your candy thermometer should read 88 degrees. Spread on top of toffee with a cake spatula. When the chocolate is still hot add your chopped pecans or walnuts.
This is a picture of the toffee when you are finished. If you want both sides with chocolate and nuts these are the steps. This is what they do with Almond Roco. Cut the toffee into squares when cooled. Dip both sides into melted chocolate and the nuts.
If you want it just like the photo double the toffee recipe. That pic has thick toffee in the center.