COAT a 9 X 11-inch Pyrex pan or a quarter sheet pan with shortening. Or spray it with nonstick spray.

POUR the Rice Krispies cereal, cake crumbs, and 1 cup of mini marshmallows into a large mixing bowl.

MELT the butter in a large pan on the stove over medium-low heat.

ADD 6 cups of mini marshmallows and stir until they are almost melted.

SPRINKLE in the white chocolate melting wafers and stir until the sauce is melted and smooth.

REMOVE the pan from the heat and pour the sticky sauce into the bowl with the cereal, cake crumbs, and mini marshmallows.

STIR to incorporate the dry ingredients into the sauce. Add the jimmies and stir to combine. (See notes.)

PRESS the mixture into the greased pan. Wet your fingers under the kitchen faucet and shake off the excess water. Then use your fingers to lightly press the mixture into the pan, trying to get it as level as possible.

DRY the Rice Krispies treats for about an hour. Chilling in the refrigerator can speed up the process.

CUT the treats into squares.

MELT the reserved white chocolate in the microwave until it is smooth. Scrape it into a zip-top baggie (or, better yet, use a decorating bag). Cut a small hole in one corner of the bag.

DRIZZLE the chocolate back and forth across the Krispies treat squares.

HEAT the melting wafers in the microwave at 50% power for 30 seconds. Repeat in 15-second intervals until it is smooth. Dip half of a cut treat into the chocolate and shake off the excess.

SPRINKLE again with jimmies if desired. Give the white chocolate 5 minutes to dry.

SERVE the treats right away.