Preheat the oven to 425 F. Line a half-sheet (the rimmed baking sheet you probably use for cookies, 18X13 inches) with foil and grease the foil. Set aside.

Lightly toast the oats and then dump into a large mixing bowl. Mix in the Rice Krispies.

If you have a kid helping, be sure to have them out of the way for the next step--boiling sugar will seriously burn. Combine the sugar, butter, water, light corn syrup and salt in a large saucepan. Bring to a boil with a candy thermometer attached to the pot. Boil for 5-10 minutes, until the the mixture reaches 250F. Pour it over the mixed cereal and toss to combine. Add 1 1/2 cups of the miniature marshmallows and toss to combine those.

Press the mixture into the prepared pan. I used a sheet of parchment paper which worked really well. Sprinkle with the remaining marshmallows and the chocolate chips (here is where your child can start helping again!). Sprinkle with the coarse grey sea salt to taste.

Bake the bars for 4-5 minutes, until the marshmallows puff up and get that awesome toasty color you associate with marshmallows roasting over a fire. Remove and let cool for 10 minutes. Cut the bars while they are still a little warm--it will be sticky and messy probably no matter what unless you are a lot more talented than me!