Combine sugar, Karo syrup, and water in a medium saucepan.
Do not stir.
Cook over medium heat until it bubbles and then turn up to medium-high heat to a dark caramel, swirling as it begins to brown to distribute the sugar.
While the sugar and water are going at it, heat up the cream in a saucepan or microwave until just warm.
Take your sugar and syrup mixture off the heat and add 3 Tbsp of room temperature butter.
Whisk the butter in, being sure it's totally combined.
Add your warmed cream and whisk vigorously and add the salt. Set aside.
In a large saucepan, melt the remaining 2 Tbsp of butter over low heat. Add marshmallows and stir until completely melted.
Remove from heat and add the caramel and stir until thoroughly combined.
Add Rice Krispies. Stir until well coated. Using a buttered spatula or wax paper, evenly press mixture into a 13x9x2-inch pan coated with cooking spray.
Allow to cool and then cut!
