Warm large sauce pan to medium heat and add butter to brown. Butter will foam and sizzle as brown specks appear on the bottom of the pan. When the aroma of the pan is nutty and the bottom of the pan is a toasty-brown color, add marrshmallows and turn off heat. Stir together until smooth.
In a separate large mixing bowl (or extra large if you have it) combine cereal, salt, and butterscotch chips. Pour warm butter and marshmallow mixture into cereal bowl and mix together with spatula.
Create a non-stick surface with a light coating of butter or with nonstick spray in a 9x13 inch baking dish. Press cereal and marshmallow mixture into dish with spatula until the top is a smooth, even layer. Top with additional Jacobsen salt. Cool completely before cutting into 12 squares. Wrap leftovers in plastic wrap.
*If you do not have Jacobsen salt on hand (highly recommended), use another high quality sea salt or finishing salt.