1/2 cup pretzel chocolate candies, such as pretzel M&M's, very coarsely crushed
1 cup mini pretzel twists
1 teaspoon flaky sea salt
Preheat the oven to 300 degrees F. Line a baking sheet with parchment paper.
In a large bowl beat together the brownie mix with the melted butter, egg white and 1/3 cup water until well combined. Use a rubber spatula to fold in the chocolate chunks and crushed candies.
Pour the batter onto the prepared baking sheet and use an offset spatula to spread into an even 1/4-inch-thick layer. Scatter over the pretzel twists and gently press into the top. Sprinkle with the sea salt.
Bake until crisp looking and mostly dry, 30 to 40 minutes. Then turn off the oven and leave the brittle inside until completely cool and dry. Break apart and serve.