The last component of these rice krispies is the decadent dark chocolate ganache! If you need to make the ganache in advance, it can be covered and stored in the fridge for up to a month. Heat 3/4 cup + 3 Tbsp of heavy cream in a heatproof bowl in the microwave for 45 seconds, until it's just beginning to bubble.
Gently pour 1 1/4 cups of dark chocolate chips into the heavy cream. Make sure the chips are fully covered with cream. Let the mixture sit for 1 minute. If you want to use milk chocolate to make the ganache, use 1/2 cup (120g) of heavy cream, and 2 cups milk chocolate (350g).
Stir slowly until the cream and chocolate are combined and the mixture is smooth. If any bits of chocolate aren't fully melted, heat the mixture again for 15 seconds and stir until smooth.
Mix in 3 Tbsp of unsalted butter, 1 Tbsp of corn syrup, and 1/4 tsp fine salt until combined.
Remove the chilled rice krispies from the fridge or freezer and pour the ganache on top of the caramel. Smooth into an even layer, then set aside to let the ganache cool and set. If you want a more textured look like mine, let the ganache cool to room temperature before spreading it on top of the caramel.
Add a sprinkle of flakey sea salt on top of the ganache, then enjoy! These bars can be stored at room temperature in an airtight container for up to 2 days, or in the fridge for up to 5 days.