Tuna, catnip, and egg whites quickly come together to make these tasty treats.
Preheat oven to 325°F. Line a large baking sheet with parchment paper or a silicone baking mat; set aside.
In a large bowl, beat egg whites with an electric mixer on high speed until stiff peaks form (tips stand straight).
In a food processor or blender, combine tuna, 1/4 cup beaten egg white, and catnip. Cover and process or blend until completely smooth (keep the machine going; it will get there). Gently fold tuna mixture into remaining beaten egg white until just combined.
Transfer mixture to a piping bag fitted with a 1/4- to 1/2-inch round or star tip. Pipe 3/4-inch dollops onto the prepared baking sheet.
Bake 20 to 25 minutes or until dried and treats easily release from the parchment. Cool treats completely before storing.
*It is important to use solid light tuna and not chunk light tuna. We found that chunk light tuna is softer and moister, resulting in treats that don't bake properly.
Storage: Transfer cooled treats to an airtight container. Store at room temperature up to one month.