Melt chocolate over a double boiler or on very low heat (this works for me without scorching but you just have to know your stovetop). You can also do this in the microwave in 20 second intervals, stirring between each interval until completely melted.
Add vanilla and crushed pretzels. Stir.
Spread the mixture evenly onto a parchment lined baking sheet. Spread it thinly, but not so thin you can see the paper. Finish with sprinkle of kosher salt.
Refrigerate for 30 minutes-1 hour or until completely set. If you don't want to refrigerate, you can let it harden on the counter but it will probably take 4-5 hours.
Break into pieces. If you want them more uniform you can use a sharp knife. Store up to 2 weeks in the fridge, 1 week on the counter, or serve right away.