Prepare the pan by lining an 8-inch square pan with parchment or wax paper, allowing some excess to hang over the edges.

Warm the nut butter in a microwave-safe bowl for 15 to 20 seconds if too thick, then stir to achieve a creamy consistency.

In a large mixing bowl, combine your cereal, warmed nut butter, sweetener, optional salt, and protein powder. Stir until well incorporated.

Transfer the mixture to the lined pan, pressing down firmly with a second sheet of parchment paper to compact it tightly.

Chill in the freezer for about 30 minutes, or until firm enough to hold its shape when cut.

Remove from pan using overhanging parchment, slice into desired sizes, and store as preferred.