Preheat the oven to 400.
Line a large bar pan with parchment paper, cover with pretzels
In a medium saucepan melt the butter over medium-low heat. When it begins to bubble add the brown sugar. Stirring occasionally let the butter/sugar mixture meld together and brown. This should take about 3 minutes. Do NOT let it boil, you will have sticky goo that is no good. When you have a nice, brown caramel pour it over the pretzels, slowly and evenly. You can then use a spatula to spread it out, you have to work quickly and gently. It hardens fast so even pouring is the best method.
Bake the sheet for 5 minutes.
Remove the sheet from the oven and sprinkle the whole bag of chocolate chips evenly over the mixture.
Place back in the oven for about 45 seconds. If you let it sit there too long the chocolate will burn.
Remove from the oven and use a silicone spatula to evenly spread the chocolate over the top.
Sprinkle with sea salt and refrigerate for a minimum of 1 hour.