Mix together all ingredients except cereal and Nutella and pour into 2 qt. ice cream maker.
Follow manufacturer's directions.
Warm Nutella in microwave slightly. Add half of Nutella to cereal and stir to coat
Spread on a baking sheet and place in freezer to firm up.
After ice cream has set up, stir half of Nutella crunch into ice cream.
Put a layer of ice cream into a container, drizzle with half of the remaining warmed Nutella, add half of remaining crunch and repeat.
Notes
For the smoothest texture, make sure your ice cream base is thoroughly chilled before churning. A cold base freezes more quickly and creates a creamier ice cream.
Warm the Nutella slightly before swirling it into the ice cream. This makes it easier to drizzle and creates beautiful ribbons of chocolate-hazelnut flavor throughout the ice cream.
Allow the Nutella-coated Rice Krispies to cool completely before mixing them in. This helps them stay crunchy and prevents them from melting into the ice cream.
Add the Rice Krispie mixture during the last few minutes of churning or gently fold it in by hand after churning to keep the cereal pieces intact.
For the best texture, let the ice cream sit at room temperature for 5–10 minutes before scooping. Homemade ice cream tends to freeze harder than store-bought varieties.
Store the ice cream in an airtight container with a piece of plastic wrap pressed directly onto the surface to help prevent ice crystals from forming.