Spray an 8x8 inch pan with non-stick spray, or butter it.
Melt butter over medium heat in a large pot. I like to use a light-colored pot since it is easier to see the butter browning without burning it. Once melted, the butter will begin to foam. As the foam subsides, solids will begin to develop on the bottom of the pan and the butter will start to smell deliciously nutty. Swirl the pan a few times while the butter is browning to make sure the solids at the bottom don't burn.
As soon as the butter is browned, turn the heat down to low and add the marshmallows. Stir continuously until the marshmallows are fully melted.
Fold in the cereal with a rubber spatula or wooden spoon and mix until well combined.
Pour into prepared pan and pat into an even layer.
Let cool to room temperature (30 minutes to an hour) and cut into squares.
Coarsely chop 3/4 of the chocolate (6 oz), and very finely chop the remaining 1/4 (2 oz) of the chocolate.
Place the coarsely chopped chocolate in a small microwave-safe bowl and heat in the microwave on full powder 30 seconds. Stop stir and heat another 20-30 seconds until mostly melted. Stir the chocolate until it is completely smooth and melted.
Add about half the remaining finely chopped chocolate to the melted chocolate and stir until completely smooth and melted. Keep adding the finely chopped chocolate 1 tablespoon at a time and stirring until it is taking a long time for the added chocolate to melt. Stir the chocolate vigorously until smooth. (You should not need all the chocolate).
Dip the Rice Krispie squares into the chocolate and place on a parchment-lined baking sheet to set. Sprinkle the chocolate-dipped portion with jimmies, nonpareils or anything else you like before the chocolate sets.
If you like, stick a straw, popsicle or lollipop stick in the treats to make Rice Krispie pops.