Preheat the oven to 325°F (163°C) and line a baking sheet with parchment paper.

If your oats are very coarse, pulse them briefly in a blender or food processor to make a slightly finer texture; this helps the dough hold together.

In a large bowl, whisk together the dry ingredients: whole wheat flour, rolled oats, ground flaxseed and baking powder.

In a separate bowl, combine the wet ingredients: cooked turkey, pumpkin puree, egg and olive oil. Stir to combine. Add 2 tablespoons water and mix; add more water only if the dough is too dry.

Fold the wet mixture into the dry ingredients until a firm dough forms. Gently fold in the blueberries so they are distributed but not crushed.

Lightly flour a work surface and roll the dough to about 1/4 inch (6 mm) thickness. For smaller training treats, roll thinner and cut smaller shapes.

Use cookie cutters or a knife to cut biscuits. Re-roll scraps and cut more biscuits until all dough is used. You should get about 24 small-to-medium biscuits depending on cutter size.

Place biscuits on the prepared baking sheet spaced about 1/2 inch apart. Bake at 325°F (163°C) for 25–30 minutes, then flip each biscuit and bake an additional 10–15 minutes until they’re firm and golden-brown for maximum crunch.

Remove from the oven and let biscuits cool completely on a wire rack; they will crisp further as they cool.

Once fully cooled, check that biscuits are dry and crunchy throughout. If any feel soft, return them to the oven at 300°F (149°C) for 10–15 minutes to dry out, then cool again.

Store fully cooled biscuits in an airtight container at room temperature for up to 7 days, or freeze for longer storage (see Storage & Reheating in notes).