Generously butter a cookie sheet, don't forget to get up on the sides. In a big saucepan (so you have room to stir it around good) melt the butter. Add sea salt and about 30 ounces of marshmallows (3 bags). Keep on low-to-medium heat, stirring almost constantly as it all gets gooey and melty and wonderful, for around 10 minutes. Turn off the heat and add in half the chocolate, stir it in to melt. Toss in the graham crackers, the other half of the chocolate, and the rest of the smaller marshmallows, and stir until it's all mixed together. (Here's where you can taste-test some and see how good this is!) Spoon it into the cookie sheet and press down to flatten. Let cool so it's easy to cut into squares before serving. I also served ours with some vanilla ice cream. If you make it ahead of time, just cover it well and leave it on the counter (for a day or two) or in the freezer (for longer) and get it out in time to thaw and cut before serving.