Grease an 8x8-inch baking pan with oil and line it with parchment paper. Cut another small piece of parchment paper. You’ll be using this to pack down the cereal and marshmallow mixture into the pan later.

Pour the cereal into a large mixing bowl.

Empty the bag of freeze-dried raspberries onto a plate. You’ll likely have a mixture of whole raspberries, crushed raspberries, and powder. Sort out the whole raspberries. Use your fingers (or pestle and mortar) to gently break up the raspberries into tiny pieces, about the same size as the cereal.

Scoop out a heaping tablespoon of the freeze-dried raspberries and set it aside. Pour the remaining crushed raspberries into the bowl with the cereal and toss together.

Grab a large pot. You’ll be mixing the melted marshmallows and cereal together in this pot, so make sure your pot is large enough to do that. I used a large Dutch oven.

Melt the butter in the pot over medium heat. Once melted, reduce the heat to low (as low as possible) and add the marshmallows. Use a silicone spatula to stir the marshmallows until they’ve melted completely and you have a silky smooth mixture. Add the black sesame paste to the pot and stir until incorporated.

Turn off the heat. Pour the cereal and raspberries into the pot. Use the silicone spatula to fold the melted marshmallows into the cereal mixture. I like using a silicone spatula because the cereal won’t stick to it. Make sure to scrape the bottom of the pot frequently, as the black sesame and marshmallow mixture tends to get stuck there.

Immediately transfer the cereal and marshmallows to the lined baking pan. I like using 2 large flipping spatulas to grab the cereal mixture and transfer it to the pan in batches.

Lay the small piece of parchment paper over the rice krispie treats and press down to pack down the treats into the baking pan. Try spreading the mixture evenly throughout the pan. Scatter the reserved tablespoon of freeze-dried raspberries over the top to give the treats a pop of red color. Place the parchment paper square over the treats again and gently pack the raspberries into the treats.

Let the rice krispie treats cool in the pan for 20 to 30 minutes. You’ll be able to cut the treats more cleanly if you let the marshmallow mixture cool.

Hold onto the parchment paper and remove the entire block of rice krispie treats. Cut into 16 squares. The texture of the treats are the best the day they are made. Store any leftovers in an airtight container for up to 3 days.