Preheat oven to 350 degrees. Prepare your pecans by placing a silicon liner on a baking sheet, and spread out the chopped pecans. Toast in the preheated oven for about 10 minutes. Prepare your other ingredients, then remove from oven and let cool while you make the toffee.
Use a large, heavy-bottomed saucepan to make the toffee *this is very important.*
Combine the butter, sugar, and salt over low heat until the butter is melted. Turn the heat up to medium, and bring the mixture to a boil, whisking constantly to make sure the bottom doesn't burn.
Cook until the caramel has reached 285 degrees on a candy thermometer, about 15 minutes.
Turn off the heat and add the vanilla. Stir to combine. Immediately pour over top of your prepared pecans and spread evenly. Do not scrape the pan.
Melt the chocolate in the microwave in a glass bowl in 30 second intervals, stirring in-between, until the chocolate is smooth. Pour over the toffee and spread into an even layer. Top with sprinkles, if desired.
Let cool for a few hours until set (can also place in the refrigerator) and then snap into pieces! Store in an airtight container.