Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.

Add the blueberries to a food processor and pulse until roughly chopped without turning them into a liquid.

In a large mixing bowl, combine the mashed sweet potato, chopped blueberries, and egg, and stir until evenly blended.

Gradually add the flour to the bowl, mixing until a stiff dough forms that holds together.

If the dough seems too dry or crumbly, add the water 1 tablespoon at a time, mixing until the dough is soft but not sticky.

Lightly flour a clean work surface and roll the dough out to 1/4 inch thickness with a rolling pin.

Cut the dough into small chew-sized shapes using a cookie cutter or knife.

Arrange the pieces on the prepared baking sheet, leaving a little space between each chew.

Bake for 25 to 30 minutes, until the edges are firm and lightly golden.

Turn off the oven and leave the chews inside with the door slightly ajar for about 15 minutes to cool and dry further.

Remove the baking sheet from the oven and let the chews cool completely at room temperature.

Store the cooled chews in an airtight container in the refrigerator for up to 2 weeks or freeze for longer storage.