Fill a saucepan with a few inches of water, and bring to a boil. Create a double boiler using a metal bowl that completely covers the rim of the sauce pan. Be sure that the bottom of the metal bowl does not touch the water. Pour chocolate into a metal bowl and stir gently using a rubber spatula.
Test the tempered chocolate by coating the back of a spoon and allowing it to set up on a piece of wax paper. The chocolate is tempered properly if it is shiny, dark, and smooth. You will have to try again if the chocolate looks dull or has white streaks.
Line sheet trays with parchment paper or nonstick baking mats.
Stir in pretzel pieces until they are immersed in chocolate.
Using two spoons, quickly scoop 1 1/2- to 2-inch clusters and place them on lined sheet trays. Sprinkle course sea salt over clusters from a high distance to evenly distribute. Allow clusters to fully set up before eating. Store in an airtight container in room temperature.