In a pan, toast the sesame seeds for 2-3 minutes. (see tip)
Set aside 1 tablespoon of the black sesame seeds.
In a small blender, add ¼ cup of the toasted sesame seeds and toasted sesame oil in the blender and blend until it forms a paste.
In a large pot, melt the butter over medium low heat and cook the butter until it starts to brown, 2 to 3 minutes. Reduce the heat to low and add the sesame seed paste.
Add the marshmallows and stir until melted around 5 minutes.
Add the cereal and quickly stir until evenly coated. Use an oiled wooden spatula.
Immediately press the rice krispies into the parchment paper or greased-lined pan.
Let cool for 30 minutes before cutting and slicing it into squares.