In a large microwave-safe bowl, combine 1/2 cup of butter and 8 cups of mini marshmallows. Microwave on high for 1 minute, then stir the mixture thoroughly. Return the bowl to the microwave and heat for an additional minute until melted and smooth.

Once melted, stir in 6 cups of rice cereal, 1 box of lemon pudding mix, and a pinch of salt. Mix until everything is well combined.

Gently fold in the remaining 2 cups of mini marshmallows and 1 cup of white chocolate chips.

Prepare a 9x13-inch pan by lightly greasing it. Pour the mixture into the pan and spread it into an even layer.

If desired, melt additional white chocolate and drizzle it over the top, then sprinkle with lemon zest. Allow to cool for 30-40 minutes.

Once set, slice into squares and serve.