Preheat the oven to 250°F (120°C).
Add the crispy cereal and pecan halves to an extra-large mixing bowl and gently combine.
In a medium saucepan over medium heat, combine the butter, brown sugar, and corn syrup.
Bring the mixture to a boil and continue cooking for 2 minutes, stirring constantly.
Remove the saucepan from the heat. Stir in the vanilla extract and baking soda until the mixture becomes light and foamy.
Pour the warm praline mixture over the cereal and pecans. Gently fold with a rubber spatula until everything is evenly coated.
Spread the coated cereal mixture evenly onto two large rimmed baking sheets.
Bake for 45 minutes, removing the pans every 15 minutes to stir the mixture.
Transfer the finished crunch to wax paper and allow it to cool completely.
Once cooled, break it into clusters and enjoy.
