You've probably suspected this, and it's true. The recipe for marshmallow treats has changed over the years. These days, the recipe on the side of the box has less butter and a different proportion of marshmallows to cereal. How do I know this? Because I have a recipe from the early '80s right here.
The composition is not radically different. The earlier recipe had 4 tablespoons of butter and 5 cups of cereal. The current version has 3 tablespoons of butter and 6 cups of cereal. I find the difference noticeable and plan on using the higher butter recipe from now on. I've also turned these into brown butter rice krispies treats by browning the butter.
Marshmallow Rice Krispies Treats From the Eighties -- aka Brown Butter Rice Krispie Treats
4 tablespoons butter (salted) or use unsalted butter and add a pinch of salt when melted
1 (10 oz ) package big marshmallows or 4 cups of the small type
¼ cup peanut butter (optional)
5 cups Rice Krispies cereal
Have ready an 8 inch square metal pan. In the past I’ve used a 9 inch or 13x9 inch, but I like the look of tall krispie treats, so these days I use an 8 inch pan.
Rub a large saucepan or Dutch oven with butter to prevent sticking. Set over medium heat and melt the butter completely until it just starts to brown. This will happen at a different rate of speed depending on your stove. If it starts browning quickly, remove from heat, swirl the pan, and put the butter back on at a very much reduced heat. Be careful not to burn it.
Stir in the marshmallows and reduce heat to low. Stir marshmallows until they begin melting. When melted, add the peanut butter (if using) and cereal and stir until coated.
Transfer mixture to pan. Let the treats cool completely then lift them out of the pan, place the slab on a cutting board and score into giant size squares.