Kick your krispies up a notch!
First, brown your butter in your pan or dutch oven. To do this, set stove to medium heat. Melt butter, stirring frequently, until butter is a dark gold/amber color. It should smell nutty and there might be little bits of brown in your butter—that's all good!
Once the butter is browned, add sweetened condensed milk, vanilla, and salt. Stir until well combined. Turn down heat to medium-low.
Add 10 ounces of mini marshmallows to the pot and stir with your butter/milk mixture until everything is melted and smooth.
Add your Rice Krispies and stir until thoroughly combined. Then, add the remaining 5 ounces of marshmallows—you want these to keep their shape to add some texture, so be sure the Rice Krispie mixture isn't so hot it will melt your marshmallows.
Carefully pour the Rice Krispie mixture into a 9x9 dish. Take a piece of parchment paper and run it over the top of the dish to perfectly smooth out the Rice Krispies. You could also lightly spray the back of a spoon and smooth the top out that way.
Wait a few hours until Rice Krispie treats are thoroughly cooled, then cut into desired number of servings. If you want GIANT treats, I think 9 is perfect.