Line a baking dish (9×12 or similar) with foil, spray the foil with non-stick spray.

In a thick-bottomed saucepan on medium-low, dry toast the pecans for 3 minutes then add the butter and allow it to melt. Next, add the cream, salt, vanilla, and sweetener. Bring to a medium-low boil (6-9 minutes), stirring frequently. Using a digital or candy thermometer, allow the temperature to reach 285°F then remove the pan from heat.

Pour the toffee into the prepared dish and chill until firm (30+ minutes).

Melt chocolate in the microwave (15-second increments) then pour over the candy. Return to the refrigerator to chill a bit then add some chopped pecans and flaky salt as a garnish before it has completely hardened (this allows the garnish to stick).

Remove the foil from pan and the toffee crunch from the foil. Use a knife to break the toffee, It will break in its own way (no perfect lines).