Line a large rimmed baking sheet with parchment paper.
In a medium, heavy-bottom saucepan over medium heat, combine the butter and sugar. Stir consistently and monitor the temperature aiming for 285°F.
Once the toffee reaches the desired temperature, pour it onto the prepared baking sheet and spread it out evenly.
While the toffee is still hot, sprinkle chocolate chips over the top and let them sit for 1-2 minutes to melt, then spread into an even layer.
Sprinkle the finely chopped pecans over the melted chocolate and gently press them down.
Allow the toffee to sit for about an hour or until completely set.
Break the toffee into bite-sized pieces and serve or store for later.