Start by washing the mint leaves and spinach thoroughly under cold water to remove any dirt or debris. Pat them dry with a clean towel or paper towel.
In a blender or food processor, combine the mint leaves, spinach leaves and liquid of choice. Blend until you achieve a smooth and well-combined mixture.
Once the mixture is smooth, pour it into silicone molds or ice cube trays, it should fill up about half of the depth of each space. I used little size ones but feel free to use bigger ones or even little cups or bowls for bigger doggos. Put the mold in the freezer to settle the green part while you prepare the purple one (make sure it stays flat).
Add the kefir and blueberries to your blender and repeat the process. Make sure the green part is frozen to the touch before adding the purple one on top if you want to get the two separate levels (if it gets mixed, too bad, it’ll be equally yummy!).
Sprinkle the catnip on top if using.
Place the molds or trays in the freezer and allow the mixture to freeze completely, usually for about 2-3 hours or until firm.
Once the frozen breath mints are fully set they are ready to be enjoyed! To store them easily in your freezer you can remove them from the molds and transfer them to an airtight container or freezer bag.