Spray an 8x8-inch baking pan with cooking spray and line with parchment.

Add the crushed pretzels and cereal to a mixing bowl. Set off to the side.

In a small saucepan with a candy thermometer attached, bring the sugar, water, and corn syrup to a boil. Whisk intermittently. Boil until the temperature reaches 235 degrees F and the color changes to a light caramel.

Remove saucepan from heat and whisk in the butter.

Once combined, pour quickly over the cereal pretzel mix. Stir with a rubber spatula to evenly coat. Then quickly pour the mixture into the prepared pan. Press into one even layer using the spatula. Allow the crust to cool before preparing the center layer.

Once the crust is cooled, add the milk chocolate and peanut butter to a microwave safe bowl. Microwave on high for 30 seconds. Stir until the chocolate is melted. You might need to microwave for another 20 seconds if the chocolate hasn't melted quite yet.

Pour the mixture over the crust and chill in the fridge for at least an hour.

After an hour, prepare the top layer. In a saucepan, melt the butter, chocolate, and corn syrup over low heat. Whisk continuously until combined.

Pour over the middle layer. Chill until set, at least an hour.

Sprinkle with sea salt, slice, and serve.